As an aside to Langdon's write up above, "Mercenaries, Spies and Private Eyes"
  1. used exactly the same ruleset as "Tunnels & Trolls"
  2. is backronymed to "Mike Stackpole's Personal Effort".

MSPE was, apparently, just as good as T&T (in that the GM was entirely responsible for what happened, so long as the players agreed - which is how a RPG system should work). I never saw the rules, though - I've always wondered how he handled spells.