Desura keys?

I think you can post them but not expect anything in return, nor can you actually do giveaways with them unless support agrees.

Also for shits and giggles and swag and stuff FIRST Y0l0

Not as a giveaway mechanic, but only as like forum or chat giveaways i guess.

You can't make giveaways for them but you could give them away in the forums

you can here