Endlessly Respawning Snow Golems on IC: 1
The Snow Golems respawn every time you enter the area
The two snow golems standing on the gates at IC: 1 respawn every time you re-enter the area. They currently make for a nice little XP farm as they're worth 5k XP each and it's so easy to respawn them. I'm guessing this is not intentional, as no other monsters in the game respawn like this (to my knowledge anyway!)