Is a P-38 the fold-flat military can opener? If so, I had one confiscated at Ottawa airport last month. I kept it in my wallet, folded flat, and threw my wallet into my hand luggage. I've done this several times without problem; this time, one of the security guards got curious about the flat rectangle that showed up on the X-ray and insisted on seeing what it was.

They were actually very nice about it - they insisted at least three times that I could keep it, as long as I went back to the airline check-in counter and checked it in. I figured the 50 cents it would cost to buy a new one didn't make it economically viable to do so (although a part of me still wonders how the airline check-in staff would react to being asked to check an item of "luggage" that was smaller than the luggage tag <img src="images/graemlins/wink.gif" alt="" /> )