Two things, though, I am very ashamed about. Once, while traveling on a Texas International Flight in 1979 From STL to DFW with two friends from college, we happened to notice that there were life vests attached to the underside of the seats and I took one.
Another time, I was with two different friends ( a guy and a girl) flying from ELP to DAL on a Southwest flight, but it was the 727 that Southwest leased from Braniff for a time. The girl had gotten cold during the flight, so the flight attendant brought her a blanket. It was one of those really nice colorful Braniff blankets - hot pink and orange plaid. Well, I just decided I had to have it, so towards the end of the flight I stuffed it into my carry on.
Well wouldn't you know it, the flight attendant came to collect the blanket. First we tried to ignore her, then we told her we gave it to another flight attendant, but she didn't buy that story for a minute. She gave us this LOOK and said "I'll be BACK in a few minutes to get it." BUSTED!!
As soon as she walked away I unzipped my carry on and had that blanket out and passed it to my friend who was on the aisle in about 1.5 seconds. I couldn't even LOOK at the flight attendant when she came back to get it, I was so embarrassed.
These days, I only take inflight magazines and swizzle sticks.