My ringtone is the dethphone ring from Metalocalypse. Thus, I have the most brutal phone EVER. I am so obsessed with that show. I even made my Courier in FA:NV into Ofdensen without even realizing it. Only after a few hours in did I realize just who my male brunette courier with glasses in a grimy pre-war business suit specializing in speech, barter, melee, and guns truly was. I think it finally sunk in when I was recruiting acts for The Tops and happened to go into 3rd person view. xD
I also have various Zelda ringtones, a few Mario and Final Fantasies, three Buffy ringtones, and two of Doctor Who. I have the Doctor Who theme song and the Tardis whooshing noise. Oh! I also have a ringtone of Dr. Horrible's evil laugh. It is awesome.