Hmm...I have a few bottles of Crystal Pepsi I'm saving for posterity's sake. I knew that stuff wouldn't take off.
Anyways, that is definitely not one of my favorite drinks, discontinued or not, but here are some:
SHASTA! (all the flavors, man I loved that stuff...maybe it's still available in some places, but not here)
RC Cola (do they still make this? I remember getting RC at Shoney's when I was a kid)
Josta (even if it was pure guarana juice)