GA for keys that I'm not sure about.. Yes or no?

I would recommend no. If you make a giveaway and the key doesn't work, you would need to find a replacement copy or take the Not Received. You can ask the winner to allow you to delete it but they don't have to accept that, even if denying you won't help them get the game.

Better off just checking your friend list to see if anyone there is interested in the game. I've found that friends tend to be more forgiving of a dud key.

Like DeltaBladeX your are better with giving them to your friends or dropping your keys in a forum.

Eiher you do it like everyone already said or you look for a small group you are in an give them away in this group. im always doing it the same way. Just write in the discription, that you are unsure about the key and that the winner should accept the conditions

It's so pity where are no way in the whole World to check game keys T_T

This nice group (it's not only for free games actually) has the rule that the winner agrees to delete the GA. However, there's also a 3-strikes rule and I'm not sure how it works in practice. The group creator says:

I don't think you need to worry about this too much. To get a strike, not only does the key need to be bad and you also need to be without a spare, but the winner also needs to report it. This happens very rarely. I don't expect GA creators to report themselves ;-)

The best way to go about it would be just create the giveaway if you have reasonably high certainty that the key is good. If you have significant doubts, using keygiveaway.com would be the better venue. That's what I do.

yeah I think that the best solution is to make a steam group and give them out there but say that it might not work (the key) or just give them out to friends or perhaps a whitelist only giveaway not so sure... I don't think that everyone would agree to delete the giveaway if ur key was duplicate. Cheers, have an awesome day!

There's a thread here in discussion called Orphan keys something. You could post the keys there (of course not the key itself, because bots, but make some puzzle out of it then) but it won't grant you any CV. So if it's lots of gamekeys I wouldn't recommend that, only perhaps for the unknown ones...
Or indeed do it for a small group you know would agree to delete if it is duped or anything

I agree with Saucisse, do it win that group if you are not afraid of getting less then 5 enteries and no CV, or if you are do it publicly with a chance of getting what the moderator said. To be honest I saw a lot of those GAs get deleted especially if you make it invite only and make a post stating there is a chance they could be bad. It is up to you on what you do but everything except just giving the keys has some possible trouble with it

Try the ninja retreat steam group. One of their rule is that the winner agrees to delete the game if the key doesn't work.

Thanks for the responses y'all!

I think I'll just post the keys I'm not sure about in the orphan keys thread. Wouldn't want someone to not read the description and then get me in trouble for not delivering a working key.