"Nucular" for "nuclear" - we can blame Jimmy Carter for that one;
Starting a sentence with "so" (e.g. most Radio 4 interviews)
Inserting "like" or, worse, "obviously" in places where nothing is being compared and even less is obvious (See above)
"Of" instead of "have" - "I should of known better"
The use of a long "A" sound instead of a totally different vowel - marled (mild); arlands (islands), marls (miles) arrs (hours); I even heard "varlant" (violent) the other day!
"Fewer" instead of "less", and vice versa
Poor syntax which leads to confusion e.g. "He bought the car on Wednesday which was faulty" (in what way was Wednesday faulty?)
No, know; there, their, they're; to, too, two
(and, just for Malcolm, if you turn a radio up to make it louder, why do you turn a fridge down to make it colder?)
Could be worse......could be Hungarian (apparently the most difficult language in the world to learn).
DM