I'm inheriting a shoal of 11 Harlequins on Friday, can't wait to get them. Always admired them in the LFS.
Glowlight Tetra's are often over looked in favour of the brighter coloured Neons and Cardinals, but are excellent under aquarium lighting and not the dealers tank lights. Pretty peaceful, can be easy to breed should you want to and are cheap as chips. One of my LFS has them in for 85p each, so a big shoal won't cost you the earth.