Thinkominos
I think I received this puzzle as a Christmas or birthday gift, but from whom I can't recall. It's been on the shelf for a while, and I remember having solved it at one time, but can't remember the solution. I'm sure that I just happened upon it randomly if I did know it.
Basically, Thinkominos is a puzzle with six hexagonal pieces. Each piece has six circles of color on the top, one for each of the piece's edges. Every colored circle on top of a single thinkomino is different, and is either red, orange, green, blue, yellow, or purple.