Try and do a karaoke theme, you can dress up for it, and have a contest where the winner gets to open their present first, and the person who comes in last has to wait until the main festivities are over. You can even go American Idol themed, where you make a stand in front of judges. Anyone could participate at that point, and everyone who at least tries can receive a goody bag filled with secret but cool items. There could be a point where somebody could record it and post it on youtube, for others to see as well! You guys could go to your local mall, and pretend you are superstars. Just dress how a singer would in a public place, (normal but trendy, with big glasses) and go out on a limb, singing for people or giving out autographs.
I got a lot of presents for my 16th birthday, but i didn't do anything as both my parents had to work on my birthday. =/