What should I do when I win giveaway and the key is not the game that it should be?

Mark as Not Received after a week if he doesnt give you the right game. What did you receive instead of Hitman Absolution?

You should ask the creator to provide you the correct game, if he refuses mark it as not received after 1 week passes, don't mark game as received even if creator asks you, because you can get suspended for not activating the game you won.

For example lately some ppl may create GAs for Pixel Puzzles Zombies and giving keys for Pixel Puzzles Japan, which was given for free, which is not cool, bad is some winners still mark received even if they didn't receive the correct game.

if you won a giveaway for game "A" but the creator of the giveaway gave you a key for another game just say to the creator "hey! this is not the game from the giveaway" if by seven days after the end of the giveaway you still dont have the game from the creator or if he refuses to give you the game just mark as not received

There's always a solution :3

View attached image.

Yeah, just let him know like faboitas said. Write something on the giveaway, his Steam profile or even add him. It could be a mistake or intentional, give hime a chance to fix his mistake if it is one.

I once accidentally gave Devil May Cry 4 instead of DMC: Devil May Cry to a winner in Steam chat. It was actually me who noticed before they did but it was too late and they'd already activated it. I then gave them the right key and they got two games for one win. Stuff like that can happen.