ThrillerBark: If you're stuck against a wall it's a Flash issue, not a game problem. The keyUp signal never got sent - just hit the key that appears to be stuck (i.e. if you're stuck against the right wall, it's probably 'd') and you'll be fine.
Always carry an explosive + regular gun. Stay just outside splash range and attack with the generators - you won't get swarmed as much.
Regular gun is for when they're really close, or for just wandering aroud. I use a sniper thing (7 range)
Fastest way to get xp from endurance: send a bunch of waves and die. Don't build any towers, traps or drop bombs. You'll get like ~300 xp for doing nothing!
PS: For below to work, mix moving forward and jabbing to keep your opponent stunned. THey may still jump over you, so don't expect every round to be perfect... just had 2 in a row tho :P
why not let players select their own difficulty for the last boss? (i.e. give it more hp, add swarming bunnies [which will make it easier by charging your rage meter...])