Desura keys

No.

On the forums you can do whatever with them. Giveaway, puzzle, etc. But not one for CV.

on steamgifts pretty much only forum drops. anyway you may have the chance to create actual giveaways on other sites.

ItsTooHard will let you make a puzzle so we actually have to work for it :P Plus most of us here love puzzles.

Gala Giveaways supports Desura giveaways