DoomRL is balanced so perfectly.
Rather than being a set of game mechanics, there is an actual world put together with rules that can be exploited.
I really admire that.
Here is a mission and I don't care how you do it, but this is a list of things that you can do to manipulate this world to get you there.
I haven't played it for a while, but it consumes me once more.
Edit:
I think it is one of the very few games where although I try to get to the end, I am enjoying the journey more than the thought I might actually beat it one day.