I call all my female characters Esmerelda, and once that's taken I call them Bertha. I don't know why. I also like calling characters names from countries they are clearly not from. In Persona 4 I called my character Jean-Paul
A really dumb trick is to choose local coop, make both of them controlled by the same keyboard and choose the same character twice. As the characters just overlap each other, and they move at the same time, you essentially get double damage per move.