You can give it to someone else. It will work.

Nope. I thing you can gift since you have the game already, you cant activeated it twice, so yoe you can give it away

hmm be mine 5 good games inside?

yep

Yep, X blades :)

Ik, so i'll start a giveaway open for 1 hour to test :)

Here is the link for this private giveaway (you're warned :))

http://www.steamgifts.com/giveaway/Ed2GN/x-blades

What did it say after you tried to activate the key?

"you already own this game" and it proposes to install it, as if the activation worked. But i theorically can't activate a game with two different keys on steam, so I don't know what happens to the new key.

[EDIT] I tried again, and the real sentence is :
"This product had already been registered.

This steam account already have this product linked with this activation code. Click Next to continue installation"

But it's a NEW key, so I don't know...

And if this work, i'll have an extra gift from Indie Gala 9 :)