Xbox One S (currently on sale at various outlets with as many as 4 free games, could throw in Xbox Live and extra controller) 4K Computer Monitor Canon PowerShot Camera GoPro Yuneec Breeze 4K Drone LiftBoard Electric Skateboard
Best Buy has a handful of 4K TVs for <500. Portable bluetooth speaker Amazon Echo Smart Watch Nest thermostat (for the practical prize lovers) iPad or Surface tablet Gas and/or Charcoal Grill Set of Golf Clubs Kayak Ping Pong Table
http://bbs.clutchfans.net/index.php?threads/4-hair-gel.189712/ It won't go through the whole $500. But a good deal regardless. And will make certain people st your event excited.
Ended up getting slammed with real work on Thursday and Friday and had to delegate this off to someone else. Unfortunately, the strippers weren't approved.