I normally go Tri-Stat, but I did use a modified D&D stat system for my Gundam RPG... A bunch of my games have been school-related, even one that was similar to persona (in that, they were mostly normal until they got to the freaky supernatural stuff). I tend to be really lax with my games, not taking health and energy into anything but a loose consideration. After all, if you get your head chopped off, (generally) you're dead.
Usually, I prefer a D6- I'm comfortable interpreting it's rolls and have been using it the longest. D20s I quite dislike. Sure, they're very common, but the variance is always so wild... Yeah, you can have skills make up for that kind of thing, but the D6 makes it more simplistic.
Recently, I've begun a multi-die system with my Sailor Moon RPG. It goes a little something like this:
Good Side:
Cats: D3, Humans: D6, Sailor Scouts: D12, Final Battle Sailor Scouts: D24
Bad Side:
Monsters: D5, Generals: D8, Bosses: D14, and Final Battle Boss: D20
By manipulating the die like this, I'm able to simulate the chances that people have against each other (though, admittedly the monsters MIGHT be higher, let's not forget how they don't usually just grab all humans. They may scare one into a corner, but... Humans be dummies sometimes. >:( ) that, at least, gives ME the feel of the show. I've had my members agree as well.
Um... Not sure what else to talk about now... Guess that's all for now! Sailor Moon says!
Cue Sailor Moon Theme.