Ear wax
Personally, I use the bent paper clip, have a couple lying on my desk right now (need a backup).
Most effective & most painfull:
Went to pull the motor on a VW once, crawled under it, & pulled the gas line. Anyway, the gas tank filled my ear up with petrol. Talk about HURT, I was running around in circles screaming, finally got my buddy to snap some vicegrips on the fuel line (had a fire going in the wood stove about 20' away, damm near removed the shop from the face of the earth).
Bad thing is, that was my good ear.
Charles