Blar!

I know, 'blar' is not a word. That's cool. My 4 year old son uses 'snuggles' as an emphatic explative, so who really cares. It's all about inflection. I say 'blar' the right way, it can mean 'huh?' or 'yup.' or 'nope' or 'godfreakindamnitalltohell... and back.' 

Try it. Use 'blar' in place of your favorite from the above list, in the proper inflection. I bet you anything people will know exactly what you mean just by the inflection.