What kind of fish are you looking for. Those under 4-in or over? Schooling fish, cichlids, etc. We all have our personal favorites.
I like large schools of small shoaling fish, like neon tetras, glowlight tetras, danios or something similar. I'll add some corydoras with them as well as shrimp. Mollies, platies and swordfish can make nice displays. Male bettas can be good centerpiece fish with any of these. Cichlids can be very interesting fish to watch as well.