"unique" looking fish is a difficult subject.

With live-bearers, I'd suggest NOT to have Betta splendens, as they tend to eat newly born live-bearers (of course, that can be a GOOD thing for population control, as live-bearars CAN and WILL often get out of hand). Definitely not good with (male) guppies, but Mollies, Platies are ok.

An all-time favourite of mine is the common bristlenose, an excellent algae eater - a little bit shy, but given the right amount of cover and feeding, they will show themselves. Do NOT get one of the larger growing common pleco's for algae duties - they grow too large for most people to keep (I'm unhappy to keep mine in a 200 liter tank that has an unusually large base for a 200 liter tank!)
http://www.planetcatfish.com/scripts...s+cf_cirrhosus

Corydoras (little catfish, up to about 2"/5cm, most of them), hardy and interesting (and eats any food falling to the bottom). Best kept in a group of 5 or more.
http://www.planetcatfish.com/scripts...hp?q=corydoras

I would also suggest avoiding the temptation to buy 1 or 2 of several different shoaling fish (typically tetras and danios) - they do MUCH better in a group of at least five, preferrably bigger groups (in nature, they often shoal in the thousands).

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Mats