If I take alphabet to mean any writing system, then it's almost impossible to decide. Armenian is like Cyrillic's art deco sister, and Mongolian is like Arabic, but written vertically, and how cool is that? Hangeul is cool just because of how it works.
I think my favorite overall are katakana though. I sometimes wish all Japanese were written in katakana, but then I remember how retardedly hard it'd be to actually read all-katakana sentences. カンジハフクザツナコトダケド、カタカナデダケカイタブンショウハマギラワシスギマスネ。