Most of the african cichlids like hard water (all of the rift lake ones do).

Most of the south american cichilds like softer water.

With a 10 gallon your friend is going to need to go dwarf cichlids only.

For softer water the "rams" or "kribs" as mentioned are a good way to go. Your big chain store such as petsmart or petco should have some.

If your water is hard the Tanganyikain "shelldwellers" as previously mentioned are a good way to go.

The more common are "brevis" neolamprologus brevis and "multis" neolamprologus multifasciatus (could be sold under either common or full name). Big chain stores do not sell them. Call around to your local stores and ask if they have "shelldwellers" and you should be able to find some. Multis are a harem fish 1 male for 2-3 females. A ten gallon can support a male his wives and their kids. Brevis are monogamous, but their territories are small enough that you could have 2 pairs in a 10 gallon with their kids.