A number of things that happen at this convention:
Cosplay
Video Game free play room (from classic to current systems), and a few arcade games
Table Top Gaming
LAN Gaming
They also have tons of contests, tournaments, panels, concerts, dances, etc.

I am running a NES/SNES Tetris tournament on Sunday, starting with qualifying at noon and a finals bracket at 1:00pm.  I will also have my game (Armed for Battle) available to demo.

Check out the website for more details.