The loose Munchkin D6 that I am not
aware of being duplicated elsewhere are Swirly Pink with white ink, and Ichor Green with white ink. Two others are duplicated by the Decay Dice, I believe, and the last is the same as Axe Cop's die.
The Target die is described on BGG as "metallic brown", and has white ink.
Picture found here (it's the one on the left):
http://boardgamegeek.com/image/992363/munchkin