The xmas cube
I don't do Christmas/holiday cards. I am, however, a huge nerd so I did something different. I think of it
as a malevolent greeting card since it burdens the recipient with a puzzle.
I mailed envelopes with a stack of 4.25"x5.5" (quarter page) cards and no explanation:
The tabs drawn on some edges are the common way to indicate that the patterns should be cut out and attached to
other non-tabbed edges.
The text and color schemes provide clues as to how the edges fit together.
Nerd note: I made this in Open Office Draw
I prepared two hints incase people got stuck (these were mostly unneeded):

The finished product
These each took me about 5 minutes to cut out and assemble as I knew exactly what I was doing
Left: The final product
Center: The first demo I did to validate the lettering
Right: The first print came out blurry because I'm a n00b (the picture is actually in focus)
I had 21 printed card decks in the final run and mailed out 18. Between the prints, envelopes, stamps, and screwups,
it cost about $50.
Pics from the field
attribution: graphics from VectorJungle.com