Tits on a Whale
1) An exclamation of surprise or shock, similiar to dayum.
2) A dismissal of something unhelpful or useless
1) A) I just won a new car!
   B) Tits on a whale, that's sweet!
2) A) Hey guys, I can play "flight of the bumblebee" at 320bpm!
   B) Yeah, except you've wasted your life learning a skill which is as useful as tits on a whale.