Cymbals, yep.  Way overused, i notice this at live shows alot.  
 
 Most uderused... I was gonna say jaw harp, but i jsut heard it on the dandy warhols album.  I play mandolin, and that instrument is underused in everything but bluegrass.  Thats why my plan is to introduce it to rock, like Jethro Tull and the flute.