I’m Poppy to my grandkids. I called my paternal grandparents Grandma and Grandma. My maternal grandmother was Aunt Betty, because she didn’t want to seem old enough to be a grandparent.
My father-in-law didn’t want to be called a traditional name, not sure why. The men on that side of the family had died fairly young, so there were no other Granddads/grandpas/whatever to be confused with. He was very much a family man, and nearly 60 when the first grandchild came along. He or his daughter decided Chief was a good name. He is a quiet, sweet man, and it seemed like a friendly fun name for him. And now there are greatgrandchildren calling him Chief, and it fits perfectly.
Maternal GPs - Gramma and Grandpa Kranzke
Paternal GM (Dad’s father died from a burst appendix in 1934) - Barn (given when her first grandchild failed to say “Grandma Brown”).
Nana and Dod, named by my oldest cousin, on one side, and Gammy, named by me, on the other.
Mom’s parents were “Grandpa” and “Grandma”. My Dad’s dad didn’t want to be called “grandpa”, it made him feel too OLD 
so he was “Daddy Jesse”. And by a child’s weird osmosis, that made his wife “Mother Jesse”, and it stuck.
Maternal: Mère and Père are technically mother and father, but all the grand kids called our Cajun French grandparents this.
Paternal: Granddaddy and Grandmother.
Both sets of grandparents were Grandma and Grandpa <last names>.
The two who weren’t dead by the time I was born didn’t really want anything to do with us. We did have a surrogate “Grammie” though, the great aunt who raised Mom.
Grandma and grandpa for both sets, and the paternals where grand[mp]a FirstName if it was unclear who we meant.
My wife has a cousin who is a new grandparent, and they spent an inordinate amount of time on what ‘cute’ name the kid should call them. I can’t remember either one, but I’m pretty sure it is something hard enough to pronounce that the kid will change it into something else.
No grands yet myself, but my nieces and nephews call my mom ‘grammy’ (dad died shortly after the first grandchild was born). My kids call her grandma, since they grew up away from their cousins and that’s how we always referred to her.
My great-grandmother was Granny Lastname, my maternal g’parents were Mawmaw and Pawpaw, my paternal g’parents were Pawpaw Lastname and Grandma Firstname (she was my dad’s stepmother). To my grandkids I’m Poppa and my wife is Gram.