Baristas that truly don't know the difference between a cappuccino and a latte.
Rarely experience this in high street coffee shops but often do in smaller non-specialists such as general cafes and in the little in-store franchises of the big names that have popped up everywhere now.
I'm sure that they consider the two in the same way as 'eggy bread' and french toast, ie. the same but with a different name - can't imagine that they'd intentionally get it wrong, but a minor thing that grinds my gears all the same.