I'd imagine the lag over tor would be terrible.
You'd want something slow-paced or turn-based.
I might try setting up something when I get my server up and running.
While likely out of favor with current attention spans, there used to be text-only statistical based strategy games back in the day people would play. Forget the classification name, but some people where really into them. Something like that would not be difficult to implement over Tor and would likely be safe to implement.
Who wants to play some fucken minecraft?