You are seriously annoying me when you want to do a big reveal in writing and you spell the interjection "Wallah!" or some similarly phonetic phailure.
It's not a made-up word that you can just spell however the hell you want. It's a French word, and it's spelled "voila." (yes, I left off the accent over the "a" -- I'M not French.)
"Voila," people, pronounced "vwah-lah." Stop fucking it up.