You may know about this already, but...
It's free. (Unless you want to pay for quicker upgrades, but you don't have to.)
It's fun.
It's called World of Tanks.
It's found here
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If you want to have fun with targets err tanks, download the client and have at it. Hell, even an aircraft modeller is having a go, so it's gotta be good. Is it realistic? Hmm... maybe not strictly so, but it is fun. You hardcore trackheads might not like it, but then again, you might.Just thought you'd like to know about it.
RobG (the Aussie one)