hamana-hamana-hamana
When you experience something so exciting, or out-of-this-world, that you just can't find the right words to say at the time to express how you feel.

This saying can be used when: a hot chick in a bikini passes you by, you've just seen a ghost, you just heard that you won the lottery, etc.
Guy 1: "Check out that babe with the huge tits in the bikini"
Guy 2: "hamana-hamana-hamana"