Well, I only just started playing this one, but so far it's pretty interesting. Requires a bit of logic and a fair amount of trial and error at the beginning, but it seems like a nice time waster. Give it a go.

Light-Bot

 

I played this before. Pretty fun, but not very hard. What's with the sudden recent influx of Kongregate games?

 

Been playing a lot of flash games recently, and I generally prefer Kongregate over other flash game sites.