Riding a bike, one finds lot of things, useful, useless, strange, bizarre, etc. I forget most of them, but here a few examples I can remember off-hand:
$10 bill (in high school parking lot)
Numerous coins,
Roll of fishing line,
Brassiere,
Long kitchen knife,
Valid driver's license,
Numerous screwdrivers,
Numerous wrenches (mostly small fractional-inch sizes),
Sockets, extensions,
Several pair pliers (some in fine condition, some not),
Gas cap to fit my car---an uncommon size,
Scissors,
1962 Chevrolet owner's manual, intact,
1981 Fiat owner's manual,
Heavy ceramic bowl in perfect condition,
Nice leather coin purse-wallet I've used for decades,
Wallet (turned over to local police),
Scissor jack for Honda (works for Toyota, too),
City+county map (from site of single-car accident),
Banana in ok condition ...