I bought DH a ninja wallet tool last year for Christmas. He was really pleased and kept it in his wallet.
Without giving it a thought he has flown with it in his wallet several times. However last month, on the way back from Cyprus his hand luggage was flagged up on the routine X-ray, opened, wallet found and wallet tool confiscated. He received a quite stern talking to, and in hindsight we both thought that was fair.
Thought I'd share, as I see these tools mentioned a lot on Christmas threads. They are a great idea, but don't forget it's in your wallet if going on a plane....