I've seen guarana tossed around on this thread, but want to add that not all guarana drinks are created equal. Having tried a few, Guaranį Antarctica from Brasil is the absolute best! They make it in Portugal too, but it's not quite the same.
I'm currently in Chile for an extended period of time and everywhere I go I see "Pap" and "Bilz" soft drinks. I have to admit I have yet to try them, probably because my husband didn't exactly give them glowing recommendations (apparently they are sickly-sweet and don't have a specific flavor)
Finally, being a native of Michigan, I have to endorse any kind of Faygo soft drink (or as we call it, "pop"), especially their grape pop.