Personally, I really like coolie/kuhli loaches - they [can] come with super-distinct markings and there's just something about them that I find really appealing. Tiger barbs have oodles of personality and are always darting around; neon tetras are absolutely gorgeous in their "simplicity" (but they definitely look best in big schools), and gouramis - as has been mentioned - are also really neat. Dwarf puffers back a lot of spunk for their size. Also the so-called butterfly fish, which hangs out at the surface with these really exotic fins spread to keep it afloat, but it usually requires freeze-dried if not live foods and may snatch up smaller fish. Oh, and clown loaches are also really cool; they have super-smooth "skin" (no scales) and they sleep on their sides out in the open somethimes. You could do a whole "tiger-striped" theme with clown and kuhli loaches, tiger barbs, and anything else that has that coloration.