The worst pain ever is stepping on a lego.

I see your lego, and raise you one tarantula hawk sting.

I see your tarantula hawk sting and raise you one golden dart frog. (seriously deadly little )

Pffff, frogs. http://en.wikipedia.org/wiki/Tarantula_hawk

I know what a tarantula hawk is.
http://en.wikipedia.org/wiki/Golden_poison_frog

However, I /will/ amend my earlier statement and raise you one box jellyfish sting.
http://en.wikipedia.org/wiki/Box_jellyfish