Press the Backspace button and then type:

marketing 	- God Mode
invis 		- Invisibility
strength 	- Drink strength potion
level## 	- Transports you to the requested level (##)
weapons 	- All weapons
potions 	- All potions
enchant 	- Enchants all weapons
experience 	- 10,000 xp.
nightvision 	- Cast night vision
nuke 		- Cast nuke
freeze 		- Cast freeze
magicarrow	- Cast magic arrow
fly 		- Cast fly
fireball 	- Cast fireball
showmap 	- Full map

Thanks to Revolution readers Nathan Robinson, Ryan Cochrane, JoshG, and SilverFox!