A fish I’d now consider a classic to keep, particularly in a planted aquarium, the Featherfin Rainbowfish aka. Threadfin Rainbowfish or Werner’s Rainbownfish, Iriatherina werneri, is one of those fish I’m happy to keep and offer to you. They’re generally considered somewhat more delicate, not a beginners fish, and are appreciative of clean water. Combine that with a naturally short lifespan (2-3 years), and suffice it to say we should be glad that this species is cultivated in large numbers for the aquarium trade and has become rather affordable. Given the short lifespan, buying rather small individuals might actually be a wise idea if you hope to maximize your time with them. This is a fish which will benefit from a diverse range of small feeds, and in particular live brine shrimp now and again. Best kept in a heavily planted tank, in groups.
As I only have had juveniles come through at this time, I encourage you to do a Google search for what they grow into as adults. I’ve included a creative commons image below, but they get even better than this!