Don't get zebra danios or neon tetras. First of all, a shoal won't fit in 2 gallons. Second, zebra danios like to have a lot of space to swim around, which they can't get in a 2 gal. Cherry barbs would also like more space than that. The trouble with livebearers is that if you get a male and a female, your tank will be overcrowded as soon as they get babies.
Sorry, I really can't recommend any fish for a tank that small. The only one I can think of is a betta, and you already said you don't want one.