Fireball, Donger, Zoe are some of my favorites and easy to find. There are hundreds of excellent candidates, and probably a lot more that. Any really will do. Check out the sponsors. Don't be afraid to order plants as 'grower's choice' or 'package deals' - even if you don't know what they are sending, they are probably sending something fairly nice. You can get interesting things that way. Tell them what size tank you are building, that helps you get the right sized specimens.