Of all the games I've played, I gotta say that I've had the most fun with the old old Castle Wolfenstien, and Spear of Destiny bosses. Back when I was a kid, those were the scariest things I'd ever fought. I didn't have nintendo or anything like that. I played these first person shooters on the old 486. I remember having nightmares for a little while after playing that game where I would be running through mazes being chased by UberMutant or Barnacle Wilhem.

UberMutant ^^ Barnacle Wilhelm
also, heres a link to pictures of the rest of the bosses
Spear of Destiny (just scroll down) :
http://www.answers.com/topic/spear-o...-computer-game
Castle Wolfenstien (once again, just scroll down) :
http://www.answers.com/topic/wolfenstein-3d
Jam it back in, in the dark.