A couple of logging chains with binders and some BIG ratchet straps from some sort of flatbed truck. Lots of porn mags, those don't get touched, just noted as I pass, kind of like all the pale yellow gatoraid bottles and thousands of five hour energy drink bottles.

Once an ax head, found on the first day of an overnighter, I stashed it and came back for it later, after the trip. On the same trip I found a camera someone must have left on their car, road back down the mountain to the campground on the off chance they were still there, then back up the mountain and on my way. they were not there, and not enough pictures on the card to find the owners. so I still have the camera.
Tons of wrenches, mostly 3/8" for some reason, some metric, mostly 11mm. And on my first tour, I kept picking up bungee cords, and finally stopped when it became apparent that I was going to be tripling my mass within a couple days if I kept it up.
Once on a roadie style ride I found a 15" crescent wrench, totally covered in thick grease, but in fantastic shape. I always carry one quick release strap with me in case I find something to strap to the frame, so I made a loop through the hole in the handle and carried it 12 miles home messenger bag style. got some neat grease stains on my jersey, but it was worth it.

And once, on the last day of a trip coming home I passed a junk shop with an old trek 560 leaning against the wall. Stopped, picked it up and it seemed so light it was like magic. Drove back the next day and bought it, and realized that you cannot judge the weight of a bicycle when you have been riding one with a load for a week. Its still a sweet little bike for 20 bucks.