From news reports of tasks that various types of rodents have been trained to perform.

Distinguish healthy patients from tuberculosis patients
Distinguish Japanese speech from Dutch speech
Fear cherry blossoms
Fear terrorists
Find land mines
Detect severed animal body parts
Regain the use of their limbs
Search for humans
Assault other rodents
Hide
Find marijuana
Take ecstasy
Find cocaine
Use cocaine
Trade in foreign-exchange and commodity futures markets