OMG, I'm obsessed with this table I made yesterday:
(click on it to see it full-sized)
Attacker's skill is the Y-axis; defender's is the X-axis. Cross-reference attacker's skill with defender's and roll that number or less on d100. Formula is Y/(X+Y) = Target Number. Against someone of equal skill, you're evenly matched. After that, your odds of success are essentially how much "dog" you have in the "fight," as it were. This was inspired by ShanG of RPG.net and his quest for his ideal dice mechanic.
I'm unreasonably enthusiastic about putting this dinosaur to work in a Top Secret-like espionage game. Why not just play Top Secret? Because... I dunno. Because I like this table, that's why.
I mean, I'd like to play Top Secret again, but I honestly think the odds of running this as a playtest of some kind are better than the odds of getting a group together to play a 30-year-old game like Top Secret. That's just the way it goes, usually. Top Secret isn't RC D&D or anything -- it's pretty crunchy, with lots of little calculations to be done and modifiers to be considered. It doesn't have the charm of a rules-light old-school classic like OD&D or T&T. There are arguably better options to serve your espionage gaming needs these days.
(I've thought about doing a retro-clone of Top Secret called Open Secret, but... then I made this table, so....)
So this, then, would be something like an homage, what with the roll-under d100 mechanic and all, but after that they don't have a lot in common. I did an embarrassing amount of work on the rest of this last night in the wee hours. It all came out in a feverish stream of skills and derived stats.