Homemade hardware costumes...whatever you have handy
The quirky and sarcastic folks out there probably won't want to shell out for officially licensed costumes and pre-fabricated dresses. Rather, they'll cast around their living rooms for materials with which to make a gamer's costume. If nothing else, it cuts down on costs. Here are some suggestions:
Option 1: Wiimote
Instructions: Wear a white, long-sleeved shirt and white pants. Draw Wii Remote buttons proportionally down your body, starting at the chest with the black motion sensor panel and working toward your thighs with appropriate buttons and D-pad. If you really want to be a smartass, reverse the order of controls, wear a headband with a torn piece of fabric attached to the top, and then tell people it's a broken wrist strap. As funny as it may sound, don't wrap yourself in a condom -- it'll lead to awkward questions and possible suffocation.
Option 2: Controller Freak (get it?)
Instructions: Wear whatever you want, but make sure to put on a huge, sturdy belt. Take every single controller in your living room (including Rock Band instruments) and attach it to said belt. Then, go around pointing various controllers at various people in an attempt to "play them." Warning: This will stop being funny after the third chick you try it on.
Option 3: Arcade cabinet Instructions: Call Activision's Dan Amrich and beg him to sell you the NBA Jam costume he made to wear at this Halloween party back in his GamePro editor days.