Tanganyakins. The best little fish out there. Especially shelldweller.
You can also watch Rachel O'Leary on YouTube. she has a really good channel about small tanks. She also sells some really cool fish for small tanks, but unfortunately the coolest fish on her channel never seem to make it to her stock list. Maybe you can email her about them.
Mollies, platies and swordtails are easy and active, and allow many options for tankmates (they can probably get along with anything you can comfortably put in a 2ft cube) I would start with one of ten and work from there, unless you are looking for an "impressive" stocking list.