ClockWords Prelude. Type a word, any word you want. Think of as many, and as long as possible, and preferably using the letters with extra ammo, to shoot the bugs that are about to steal secret documents. Addictive AND RSI causer!
Fresh game scripts: KQ4, LSL2 and LSL3! Check the Script Party topic in the Bard's Forum! Skip to new scripts
I'm not sure if this technically counts as a Flash game or not, but PopCap Games has a section where they let you play limited versions of their games for free online. Just go visit their Online Games page.