I just stumbled across this game, and it's already my favorite flash game ever:
http://incredibots2.com/
Basically, you design and control machines to complete various challenges set by other users.
It's incredibly addictive, and will eat up a huge amount of your time.
Here's my red stabby thing, about to begin the "smooth ride machine" challenge
(it's probably the most poorly designed vehicle ever to successfully complete this particular challenge )
Here it is fully loaded with a volatile cargo (if any of the orange balls fall into the green liquid, it's game over)
And here it is again, about to unload the cargo at the designated drop-off point
Anyway, I strongly recommend you give it a go, if you haven't already