A paraprosdokian is a figure of speech in which the latter part of a sentence or phrase is surprising or unexpected in a way that causes the reader or listener to reinterpret the first part; it is frequently used for dramatic or humorous effect.
Where there's a will, I want to be in it. - anonymous
War does not determine who is right, only who is left. - Bertrand Russell (attrib.)
If you're going through hell, keep going. - Winston Churchill
Some cause happiness wherever they go; others whenever they go. - Oscar Wilde
I've had a perfectly wonderful evening, but this wasn't it. - Groucho Marx
If I am reading this graph correctly--I'd be very surprised. - Stephen Colbert