There are lots of these, of course, but these are some of my favourites (quite the wrong word, but no matter):
There's nothing worse . Example: "there's nothing worse than running out of milk on Christmas day". Of COURSE there are worse things. Being boiled in oil is worse. Losing a partner is worse. Being hung, drawn and...well, you get the picture.
If you like. Someone will choose an expression, and then attribute his/her choice to the listener. Example: "it's, if you like, similar to a new way of boiling carrots". But what if I don't like? What if I can see no connection at all with the boiling of carrots? It's your expression. You use it if you want to. Leave me out of it.
At all (when used in an odd position in a sentence). The best example of this comes in one of the Pooh Books (where it's not irritating at all, of course):
Pooh (to Kanga): Are you interested in poetry at all?
Kanga: Hardly at all.
I tried this out in a building society once when asked if I wanted to open an account. It was met with stony silence.
No problem (in pubs, restaurants, shops - you name it). This needs no comment from me!
Can anyone think of any more?