I'm not sure this is the right forum to ask since both giveaways and trade section (and official store) only deal with game keys.
And if we talk about Steam trading - that's not exactly in accordance with Steam rules, and there are too many possibilities for scam. And if you do that and get burned - Steam support not only will not help you but might ban your account.
But then again - people do trade game keys for all kinds of marketable and tradeable community and in-game items, and even for money. Something being illegal (or not-quite-legal) didn't stop many people before - or ever.
