Got given a used key for a different product
I bought a key for Monster Hunter Stories 3 and got sent a key for Monster Hunter Wilds that had already been redeemed months ago. First time it happens, but extremely bothersome that I had to lose my whole weekend trying to fight customer services of both HRK and Steam Support to get the game that I paid for. At least customer support was polite and straight to the point, so that wasn't an issue.