Moving on, you guys are in luck. I got some good ones. Instead of doing a countdown to the best, I'm just going to post as they randomly come into my head. That's how good I am.
In terms of simplicity and laughs you'll receive, I have to go with the guy in the elevator in the Gangnam Style video. All you gotta do is thrust your pelvis at everyone all night and look goofy. Sounds like quite a stretch for me.
Another instant classic? You and a buddy can go as referees, while one guy waves his hands in a sign of an interception and the other signals a touchdown. For added laughs, you can wear dark, black sunglasses and carry around a walking stick. (Although, there's a good chance this one might get played out by Halloween.)
Here's another one for the ladies. It's not funny, but I think it would be sexy as hell (for me). Katniss Everdeen. I would go up to you and be like, "I'll be your sweet Peeta any day... unless you want to be with Gale after the third book. You know, like later on in life. As a second marriage kind of thing. Because I can be him too. I'll wait for you..." That's when things may get a little awkward between me and said stranger.