I use my own magic system (the current campaign is the continuance of a playtest of the magic system of
Mythic Earth -- see my sig).
I had to sell Grim Tales to cover rent a few months ago, before I got a chance to actually use their car chase rules. *pouts* When I did run a car chase, I found myself winging a lot and ignoring the whole 'distance moved' bit in favor of relative positioning and such. Don't like the d20 Modern driving rules too much.
I like the variant proposed that autofire should force a save based on the attack roll.
I've accepted that I must use the Wealth system, though I do not like it. When they started trying to game the system, I was a little overwhelmed: "Well, if I buy these five items in just this order, I'll only lose 5 points of Wealth. Hey, you buy a hummer -- it should only cost you 1d6+1 wealth -- then you give it to me, I'll sell it, then I can buy two magic items and lose only 2 Wealth. Then I'll give you one item, and since your Wealth is lower, selling it will raise your Wealth more than the cost of the hummer."
Gah!
I remind folks that nonlethal attacks can become lethal with a -4 penalty. And I suppose if it were an issue, I'd rule that cats' attacks are naturally non-lethal.
I like the Martial Arts Extravaganza house rule. I need to look for a way to implement that.