Alright this is going to get in-depth.

I'm the youngest grandchild on my dad's side of the family.
My dad's mother is Grandlady. Yes, we are southern, haha. It fits here though, she is a southern lady through and through. My dad's father was Papa, and his new wife was just her first name.

My mom's mother died before I was born, but my granddad (as we called him) re-married, and we called his new wife Grandma Jean. The rest of my family weirdly called my granddad "Beebop". I have no idea why. I refused as a kid, :p

I call my step-grandparents Oma and Opa since they're German.

My dad is called "Pop" by my nephews and nieces. Not sure how I feel about it yet...My step-mom is called Omi (since she's German) and HATES it. It's stuck now though....

My paternal grandparents were retired diplomats, so there was quite a bit of formality when it came to everything about them, from what we called them to how we conducted ourselves during meals and beyond.

They were "formally" Grandmother [Last Name] and Granddaddy [Last Name]. However, my brother and I sometimes called them "Ma and Daddy-O," which was my father/aunt's nickname for them.

My maternal grandparents are, well, country. We're talking about square-dancing, pie-making, fruit canning, deer hunting, Georgia farmers. Both are still living, in large part because they had their children very young. My grandmother was still a teenager when my mother was born. We have always called them Granny and Grandpa.

ETA: On an odd note, my paternal grandfather's mother was called "Mommee" pronounce mah-MEE, with the accent on the second syllable (as opposed to Mommy, where the accent is on the first syllable).

AWWW YAY!

Maternal Grandmother: MAH-Maw
Her late husband: Paw-Paw

Late Maternal Grandfather: Granddad
His late wife: OMG I can't remember.... did we just call her by her first name?

My grandmother's step-mother was called GiGi, I supposed for Great Grandmother.

I was not raised by my father or any of his family, so I just call(ed) them by the first names when I referred to them.

Also, since my uncle has become a grandfather, I have decided to title him the new Paw-Paw.

My mom's side of the family:
Grandmother: Big Mama
Grandfather: Big Daddy

My Dad's side of the family:
Grandmother: Grandmommy
Grandfather: Paw Paw

Some real cute names in this thread. Three of my grandparents were already gone before I was born and I only met my paternal grandfather twice before he died when I was six. The whole "grandparent" thing is a foreign concept to me. I missed out! :(

I called my mother's parents Grandma and Grandpa. I called my father's father Grandpa. (My father's mother passed away before I was born, so I never knew her, but I refer to her as Grandma.)

We called my parternal Great Grandmother GiGi for just that reason.

Mom's Parents: Grandma and Papa
Dad's Mom & Stepdad: Grandma K and Papa Nick
Dad's Dad and Stepmom (never met them): Grandpa A and Grandma A

Now that my parents are grandparents (thanks to my sister), they are Amma and Pop-Pop (my nephew gave them their names). His other grandparents are Grandpa and Grandma. He calls me Yaya and my husband Coco because he couldn't say our names when he was younger (I don't know where Yaya came from) and he thinks everyone has a Yaya.

Maternal:
My Mom's Mother: Madea
My Mom's Father: nothing, never said a word to him
My Mom's Grandfather (paternal): Pawpaw
My Mom's Grandmother (maternal): Aunt Mary...long story, but she had a lot of nieces and nephews and it just stuck

Paternal:
My Dad's Mom: Grandmommy
My Dad's Stepfather: Daddy Bill
My Dad's Father: Granddaddy
My Dad's Grandmother (maternal) Big Mama

My Mom's parents were Oma and Opa. My Dad's were Grandma and Grandpa.

When I was pregnant with my first son, I decided that my parents would be Oma and Opa (since I really didn't like my grandma so the word isn't positive my my mind).

My parents went with it and now all the grandkids on that side call them Oma and Opa.

My husband's parents go by Grandma and Grandpa.

I like this. My family is boring; I can't imagine calling either sets of my grandparents anything other than the usual "grandma or grandpa" although they were all German. I thought that it was really cool when a friend of mine who was German called her grandparents Oma and Umpa.

I had an Oma & Opa

And a Nanna & Grandad

My grandmother is Grandmother. Her husband I just call by his name. My grandfather is Granddaddy. His wife I just call by her name. My other grandfather died before I was born. My other grandmother died when I was little, but I do know that I called her Granny.

My paternal grandmother was called Gramma, while my maternal grandfather was called Granddaddy. The others were long gone before I was born. Before my parents realized that they wouldn't be grandparents, they announced that they would like to be known as be Big Daddy and DeeDee.

I was "adopted" as a grandchild by one of my friend's grandmothers (who knew that my Gramma had senile dementia); I was asked to call her Gram.