What a fun question, LOL I am sure there are TONS of things that grandchildren have dubbed their grandparents, but in my home I am 'Grandma Dee'. That distinguishes from the other grandmother: Grandma Mary. On the other side I'm still Grandma Dee and my daughter's mother in law is 'NaNa'.
My mother was 'Nona' (Italian for grandma) and my maternal grandmother was 'Nonie'. My nephew calls his maternal grandma, 'Meemaw'. Not sure of the spelling, but I know it's a southern nickname.
My request, when my first grandchild came along, ( I was in my mere 40's then and thought myself way too young to be dubbed: 'Grandma') was to be called:
Obi-wan Kenobe--from Star Wars. My daughter wasn't going for it! haha.