Rhinos and commons are quite different - I wouldn't call a rhino 'common' at all, they're nice looking fish. I hope you've got a big tank, rhinos can get more than a foot long - their size is the only thing that's kept me from bringing one home from work!
I love my bristlenose (species unknown - bought him as
A. claro, but he's larger than they're supposed to get, and he's less than a year old) for both his looks and personality. I recently brought a gold nugget (L018) home, he's starting to really show some character, and he's pretty eye catching.
I'm a huge plec fan, period - I think once you're hooked, you're hooked

I don't think I have a favourite type, there are so many I'd like to keep that it's impossible to choose just one.
Check out
www.plecofanatics.com - there's a great forum and a gallery of pleco pics, which might be a good place to start if you're looking for a new plec.