I've been sitting on this one for awhile and I can't tell you how excited I am to tell you about it. Quite possibly the coolest way to way to make weird noises, Marv is a MIDI Actuated Robotic Vibraphone created by Tim O'Keefe, Michael McIntyre, and Brock Roland at the SFSU School of Engineering.
Marv is made up by several large banks of solenoids- both for striking and dampening the keys. Marv is an extremelly well documented robot- the site has extensive technical details as well as tons of photos, links, diagrams, and videos.
I chose the above video- the night of Marv's "birth" (first succesful run) because I love, and can sympathise, with the feeling of the late night in the lab, windows dark, everyone else gone home, anxious and terrified to see if with a single press of a button, your creation will come alive.