Yep, I think all I ever found were some bolts and a couple of condoms, the occasional deceased bird, and a ancient garrison cap.
I heard some stories about other stuff, but the thought of having a dead fish Cusinart through an engine is disgusting.
Dead fish - worst we had was an F-16 eating a fat seagull. And then because they had to investigate the incident down on the line before they could release the engine to us, the motor sat, pulled, under a black tarp, on the line, in Nevada, in the summer. We had to steam clean it as we went - and we were doing that in our gas masks.
FOD walks - twice a year, we'd do a big walk, from the edge of the line, across all the taxiways, the runways, and across to the revetments. Weirdest thing found was a small piston and connecting arm, like out of a lawn mower. Dumbest thing was my commander, seeing something black sticking up out of an expansion joint and pulling on it, and pulling up about 25 feet of joint filler.