"I don't think I'm going to see that guy anymore. He's a waa and always finds something wrong with everything.
1. Waa I never knew that (on hearing the news that Bill Gates was no longer Chairman of Microsoft)
3. Waaaaaaaaaa! Since when? (on hearing the news that Microsoft had decided to give away Windows for free!!)
Also can be used to describe something positive.
Blah would be used to describe some thing negative.
EX2" I had really good waa till I became surrounded will blah people...