Fireflies
You've probably seen the cute little bugs that appear during the summer, the ones that light up and look like stars floating across the ground. In the south, they're known as fireflies. Northerners, on the other hand, call them lightning bugs.
Caramel
This is another one that's kind of divided amongst the various regions of the United States. Southerners pronounce the word with three syllables and emphasize the second syllable ('care-uh-mel'). Other areas, especially the north, pronounce it with two syllables and eradicate the second syllable that the Southerners emphasize (kar-mel).
Pajamas
This mostly refers to the second syllable in the word, mainly how the 'a' sounds. Southerners pronounce the word so that the 'a' sound is long like the 'a' in the word 'father.' Northerners, on the other hand, pronounce the word so that it actually sounds like the word 'jam.'
Pen
You'd think there wouldn't be discord on what seems to be an easy word. Southerners have one of two ways to pronounce the word, either as 'pin' or like 'pyen.' The North and other regions typically pronounce it just like it should be, as 'pen.'
Coke
Almost unanimously across the southern part of the United States, the generic term for a sweetened carbonated drink is 'coke.' This acts as an umbrella term, covering all the different types of soda, not just Coca-Cola. Meanwhile, most Northerners call soda's 'pop,' though some in the northeast just call them 'soda.'
Water Fountain
You remember those things you drank water out in the hallways of your school? Well, most Southerners and Northeasterners call them water fountains. Most Northwesterners call them drinking fountains. There are also a few places up north that call them bubblers.
Anything That Ends With a 'G'
Okay, so if you've ever really talked to a Southerner, then you might have noticed that words that end with a 'g' typically cut off the 'g.' Fixing becomes fixin, going becomes goin, going to becomes gonna, and the list can go on and on. Most Northerners pronounce the 'g's in words.