Hidden treasures? Uh....
Well I don't know how hidden it is and I've already mentioned it before but Space Miner: Space Ore Bust is pretty damn good. I played through it again the other week when I flew down to LA and it still holds up.
[youtube=560,345]uYKpZZnlm7A[/youtube]
Again, not hidden but I don't see it mentioned enough - iStunt 2. BTW there's iStunt 2 Insane Hills and it's free
[youtube=560,345]_H95jePoMkY[/youtube]
And if you liked Transport Tycoon, then give Virtual City a try. I've been dicking around with this one for the past week.
[youtube=560,345]TFX4TZcM75o[/youtube]