The title is self explanatory, so I'll just give mine:

1. AB (Angelic Buster) - It's clean, it's organized alphabetically, and it's fun to say

2. DrK (Dark Knight) - DrK can be read as dark, wich I find fun, and it looks like Dr.K and he has tons of self heals so it works thematically.

3. BaM (Battle Mage) - I imagine that's how the TP sounds. That class seems like BAM