I have a couple of ideas that haven't been mentioned yet. For my older son we had a mexican party, where they had a "margarita bar" (fruit slushies in cool margarita glasses) and we had a burrito/ taco bar. He also did a pinata (even at 15)They also did the sombrero hat dance. And of course that Mexican favorite "Karaoke"

The teens really seemed to like it even if they had to be "cool"
The last party for my younger son (turned 11) was a Jumanji party. We had the movie, so we had to preview it. First off the kids got there and "made" their own popcorn:

took a plain lunch sack and decorated w/ markers and/or stickers, added popped corn then sprinkled on a topping (I had cinnamon/sugar, cheddar cheese, spicy nacho, and butter flavor) then they picked out a drink (i choose flavored water so there would be no stains on the carpet). We then started the movie. At certain points in the movie it would be time for a "movie inspired" game. The different game ideas we had were Jungle Music Rockin' (where they had to dance until the jungle music stopped, and then freeze 'til it started again. If you moved you were out the last one standing got a prize. Another one was to find the "jumanji" dice in the sand; a big bin filled with sand that the kiddos had to dig through to find a die (only 1 per child and everyone got one, so they all got a small prize) the other one was a mini treasure hunt with silly clue to find other clues , and everyone would get a prize at the end of the hunt. The prizes were Jumanji themed; like Fruit striped gum (w/ the zebra) monkey headed pens, big gummy snakes. My son also wanted a pinata, so we did that too during an intermission (stuffed the pinata with a little bit of candy, jungle themed erasers,hair combs, a few stickers, and rub on tatoos). The breaks in the movie were great, it helps the more energetic kids release a little energy. After the end of the movie we had cake and presents (I made a jumanji gameboard cake that was so cool!)
The kids each got another brown lunch sack to put their prizes, and pinata loot in as a goody bag. Cool party cost less than $60 for 10-12 kids.
The timing also worked out great, 2 hrs for the movie 5-10 min for each intermission/game, and the 15-20 minutes for cake and presents and the kids were out the door in 3 hours total!
Actually most of the kids were out the door , but the few neighbor kids stayed and helped break in the new toys!

Kept kiddo busy while we put the living room to rights.
I have to say I LOVE giving my kids parties......I never really had them growing up, just family or a girlfriend to stay the night, so I go all out to make my kids' parties good memories. That doesn't mean I will spend a fortune, I won't. They get one BIG birthday party (16th) a big Graduation party and then the last of the parties party, their wedding, if they so chose (that we'll be paying for at least)