I'm playing Persona 4 just now. An RPG by Atlus that's part of the Shin Megami Tensei series. It's pretty damn sinister though, since the battle systems goal involves exploiting an enemies weakness.

For example, if I strike an enemies weakness, that enemy is "Downed", and I get a free turn in right away. I Down all the enemies, I can rush them and then proceed to tear them apart in a single all out attack.

Flip-side though, it works in reverse. Kanji for example, is weak against Wind. Meaning that if an enemy strikes my whole party with a Wind attack, Kanji gets downed, and the enemy gets another turn in, usually downing someone else (And getting another turn) if they have more than one elemental attack.

It's pretty damn hard (But people say it's easy compared to other SMT games), but I have to say that I'm loving it to bits. It's slow-paced though, I'm only at the fourth dungeon (And the dungeons are pretty small in overall size) and I've clocked damn near 45 hours on it.