My mom goes by Oma, and my Dad, for the short year he lived after my nephew was born, was Opa. It's easy for the kids to say and spell.
"Blue" is my family nickname, so my niece and nephew were taught to call me "Auntie Blue". But when they were little they couldn't quite pronounce it, so I became "Annie Boo". I LOVED that name so much, but unfortunately it didn't stick. Now I'm "Auntie Blue" with my niece, but my nephew (who is about to turn 14) has just recently started calling me just plain "Blue" because it's not manly to say the "auntie" part and (as he informed me recently) he's "pretty much a man now".
Just typing that out right now gave me such a rush of affection, I love those kids so much, they can call me whatever they want! LOL