I know I probably am BU but it really winds me up how people use 'brought' instead of 'bought' -the verb to bring and to buy are completely different and have different meanings it's not hard to use the right one!!
The other one that really winds me up is how a lot of people use' I should of' instead of 'I should have' -of is not a replacement for have it's just wrong!
Is it just me? What other common errors annoy you?