I know its gonna sound petty but when americans pronounce words differently to british people..... and are adamant that we are wrong. (not all americans.) 

For example, I enjoyed a trip to the states a couple months ago. I wanted to check the english football scores and asked a local if he knew of any football bars and explained that i wanted to know premier league scores (Premier, pronounced Prem-yer). I kid you not the guy replied "Oh you mean the Premier league" (Premier, pronounced Prem-ear) Every british football fan just cringed as did i and the few mates i was with.

http://dictionary.cambridge.org/pronunciation/english/premier

The english vs american pronunciation. it makes me physically cringe when i hear it. sorry americans i can deal with the rest of it just not this.