A few questions first:
1. What is your stocking list?
2. Size of tank?
3. What are you looking for... algae cleaner, looks, monster?
4. Are you looking for one that has color, patterns, or just a big bruiser?
A few options that will work well for you... Panaques, pseudacanthicus, megalancistrus, ancistrus, or possibly leporacanthicus.