*Note: I snuck in more than 30 places to go here :-)
1) Go to the Mutter Museum (19 S 22nd St). It's a museum of medical oddities and it's really cool, but certainly not for the faint of heart. Ways to make this more awesome: Have your first (ever in your life) date here...crazy pre-meds. Or just take any date - if he/she can handle it, you may have a keeper.
2) Go to the Macy's in the Wanamaker building (1300 Market St). See the giant pipe organ and have a photo shoot with the eagle statue. If you're from out of state (over 250 mi away), visit customer service and show them your Out-of-State drivers' license or photo ID and and get a savings pass. Then go shopping.
3) Go on a search for authentic Mexican food (Philly isn't known for it, and you're certainly not going to find it at one of the expensive places in Center City). The closest thing you will find is Taqueria Veracruzana (9th and Washington) or one of its neighbors around the corner on 9th. [Update 10/8/17: more Mexican restaurants have opened up around the Italian Market; there is also a good truck around 4th and Washington] Ways to make this more awesome: go late at night, they're open til midnight!
4) Go to the Italian Market. Just go. When you come home, people will ask you if you went here and also if you saw the Liberty Bell, and if you ate cheesesteaks.
5) Go to Pat's and Geno's. (9th and Passyunk) Preferably late at night while you're wasted and you have a DD. Ways to make this more awesome: if one of the workers asks you or one of your friends out (AND you get a phone number). if you manage to finish a second cheesesteak. if you have a friend with a truck and you eat your meal seated in the truck bed. I personally prefer Pat's because Geno's political rhetoric is too much for me. Some Philly natives say that both suck and not to go, but it's something you need to experience once just so you can make the call yourself.
6) Go to Jim's (4th and South Streets) and Tony Luke's (39 E Oregon Ave) for steaks. Compare to Pat's and Geno's. Make your own judgment. If you're near Manayunk, I also recommend Chubby's (5826 Henry Ave) - see this post for the accompanying anecdote. Ways to make this more awesome: if you're in Center City, go to Franklin Fountain (116 Market St) for dessert. If you're in Manayunk, go to Custard and Cakes Creamery (5461 Ridge Ave) for dessert.
7) Go to the Philly Pride Parade (but skip the parade part and go to the festivities on Penn's Landing.) Ways to make this more awesome: join a friend with a boat who is willing to sail while you throw beads to the people on the landing from the boat. It's amazing.
8) Go to Oscar's at 15th and Sansom. It's a great little dive bar in Center City. Cash Only. They make the best, most dangerous Long Island Iced Teas in the city. One will get you drunk. Two and you'll be ready to blow some dude named Payaso in the back of a van. Ways to make this more awesome: hook up with someone in their broom closet (and remember mops and brooms aren't going to judge you or be voyeuristic). Participate in the Sharpie conversation in the bathroom stall. [update 10/8/17: the bathroom no longer has as vibrant of a bathroom stall Sharpie conversation because they took the second door out.]
9) Go to a Steven Starr restaurant. His restaurants are, in my opinion, a Philly staple. I really like Pod, and I've heard great things about Pizzeria Stella. Continental is also a favorite of mine, but I never leave there full, so make sure you plan dinner #2 immediately after.
10) Go to the Penn Bookstore. It's just a Barnes and Noble, but you can feel slightly bougie and Ivy League for about 10 minutes. Or longer if you stay and read in the aisles.
11) Erin Express. This is an all day bender that takes place during two Saturdays in March right around St. Patrick's Day. You wear green, start the day off with kegs and eggs, and drink all day. Ways to make this more awesome: pack your own booze or you will find yourself losing your buzz and all your money to the bars (the specials aren't always that great, what Erin Express is about is the atmosphere). Get on one of the buses and drink what you brought in the back of the bus. Don't bother getting off the bus, just make new friends and chill. If you're really ballsy, you can also sell beer in the back, which is another easy way to make friends.
12) Go to the gayborhood and enjoy the wonder that is the "gay pour" (strong drinks, a splash of mixer just for color.) If you want to dance, Go to Tavern on Camac (243 South Camac Street) or iCandy (254 S 12th St). Everyone talks about going dancing at Woody's but I find that the best dancing is to be found at Tavern on Camac and there's never a cover. I've also heard good things about Voyeur, but I haven't yet experienced if firsthand. Ways to make this more awesome: get pizza afterward at Homo Hut (aka 13th Street Pizza, and yes, people really do call it Homo Hut). But, if you're not getting the macaroni and cheese pizza, don't bother because otherwise then you're just going for ambiance. Make sure you're lucid enough that they don't overcharge you, and make sure you have cash. [update 7/29/15 - Homo Hut failed a health inspection and has closed down].
13) Sonic (2201 E Butler St). Not many people realize that there is a Sonic in Philadelphia. It's right of the Betsy Ross/Aramingo Exit. In the summer, they're open until midnight.
14) McGillin's. This is the oldest continuously operated bar in the city, and one of the oldest in the country, located at 13th and Drury Streets. If you're going on a Friday or Saturday, you'll need to get there by 8pm so you can get a table. The food is good, the prices are reasonable and the ambience is fun and positive. Ways to make this more awesome: go for karaoke night (Wednesday or Sunday). Make new friends and enjoy the decor. Or, you can be legen---wait for it---dary and bring a friend who is so drunk that they can't actually get in (which, by the way, you have to be wa-a-a-aaaasted to not be allowed in).
15) Lorenzo's Pizza on 3rd and South Streets. They're open til 3am. Pizza slices bigger than your head for $3 bucks. Cash only.
16) Tea Talk at 10th and Spring Streets. If you like boba (aka bubble tea) this place does it well. I always get the jasmine flavored one. [update 7/29/2015: this establishment is now called "Tea Chat". The tea is still just as good][update 10/8/2017: Tea Chat is also closed. I don't know what is in its place now, I'm sorry. There is a place next to the Wawa on 36th and Chestnut Streets in University City that has decent boba].
17) Barcade at 1114 Frankford Ave. Do you like retro video games? Do you like arcades? Do you like alcohol? Then Barcade is where you should go. It's not like Dave and Buster's where you can get tickets and come home with things you totally don't need but want anyway, but you can come back with warm feelings of nostalgia.
18) Brauhaus Schmidt at 7th and South Streets. All the German Beer, and you can even get Das Boot (a 2L boot shaped glass filled with beer). The food and appetizers are unique and all fantastic, and the waitresses dress in German barmaid costumes to give the place an authentic feel. I always have fun when I go, even if I'm the DD. Ways to make this more awesome: go with your coworkers and be shocked by the unexpected people who put away the most beer in the least amount of time (beer ninjas).
19) Underdogs at 17th between Sansom and Moravian Streets. They have all kinds of hot dogs, and they're good whether you're drunk or sober! [update 10/8/17: Underdogs is closed. Last I heard, there was a french fry restaurant in its place, but I have not gone to verify personally].
20) Brunch at any of the following places if you're into brunch and hate to wait: Valanni (12th and Spruce) or Jones (7th and Chestnut Streets). The food is good, the service is never rushed or hungover (at least not obviously so), and the atmosphere is good. Best of all, you don't have to languish in a waiting area for 45 minutes before getting seated! Red Owl Tavern (4th and Chestnut Streets) is good as well, especially for their bottomless Bellinis, but I cannot attest to wait time.
21) If you're interested in ceramics, check out The Clay Studio (2nd Street between Race and Arch Streets) and take a class. They are a full ceramics studio - this is not one of those places where you paint pots that other people made...here, you can make real art from start to finish. And once you've taken one of their classes, you can sign up for open studio time and come in on your own time.
22) Chris' Jazz Cafe (1421 Sansom St). The food is amazing, happy hour is fun, and the shows are good. This is a great place for a date night or even a quiet happy hour to yourself to grab dinner and a drink, hear some music, and clear your mind. Ways to make this more awesome: go alone, make friends with a band member and talk music over drinks.
23) Morgan's Pier during the summer when it is open (221 N. Columbus Blvd). I certainly enjoy getting a nice drink outside by the water in the summertime with friends - they also have ice cream and hot dogs. Can't get any better than that (unless you add sex, and that would be entirely possible since you could probably meet someone there who could help you with that).
24) Go shopping for a craft project at Blick (13th and Chestnut). This is a really good art supply store that has everything! If you're into DIY/making your own art, go here.
25) Famous 4th Street Deli (4th and South Streets). For awesome deli food and portions that will last through the apocalypse. Ways to make this more awesome: go in your pj's.
26) For some bangin' falafel, Mama's Vegetarian (20th Street between Market and Chestnut Streets). This place makes the best falafel sandwich in the city. Just remember, they're closed on Saturdays and it's cash only.
27) Get dinner at Moshulu (the big boat restaurant, 401 S Christopher Columbus Blvd) if for no other reason than to be able to say "I'm on a boat !@#$%^&* don't you ever forget" and not have it be entirely out of context. The food isn't amazing, I won't lie, but the ambiance is good and you should go once.
28) 4th of July fireworks at Drexel park, 32nd and Powelton Ave. If you want to see the 4th of July fireworks, but do not want to deal with crowds on the parkway, I recommend camping out in the afternoon with a picnic blanket and some foods and beverages. This has become a more popular occurrence every year, there is good energy and a great view of the fireworks.
29) Aloosh Restaurant (36th and Lancaster Ave). This is a newer restaurant and hookah bar - the food is amazing, the ambiance is good, and you can hookah for a reasonable price. This is a good place to take a date and actually have a conversation or go in a group with friends. [update 10/8/17: this place is closed. but you can go to Ed's Wings and Pizza at 35th and Lancaster. They do not have hookah, but their wings and pizza are bomb.]
30) Picnic in Rittenhouse Park. (Between 18th and 20th Streets, on Walnut St) It's fun when the weather is nice and the people watching is interesting. Ways to make this more awesome: Have an awesome friend who lives a block away. add vodka.
If you want EVEN MORE things to do in Philly, check out my collaborating bloggers' posts!