a small piece of brass on a bicycle

if you come across a lot of bicycles, snip off the brass valve off the innertube

also lots of brake levers are made of aluminum. smash off with a hammer, or bend off with the end of a closed loop wrench

platform pedals are made of aluminum, but removing the steel spindle inside requires popping off a plastic end cap and removing a bolt with the right size socket

lots of seatpost are also aluminum and can be removed with via quick release but you need an allenwrench to remove the seat



those are the only easy-to-get crap off a bike i can think of atm