A topic to make me think. Hm.
I know it's not all about the battles, but the most unique aspect of my game (mechanics-wise) is probably the combat. You control up to 3 characters in real time (and sometimes there's a fourth AI-controlled NPC) against up to 4 enemies. Each PC can either be in Attack or Support mode--in Attack mode, they run to the frontlines to fight the enemies, while Support characters stick to the rear and cast magic. Your attack mode characters inflict less damage, but of course the mellee attacks also cost less MP/SP. If they're taking too much damage, you can attempt to dodge enemy attacks by jumping backwards, but if you retreat too much then you put your Support characters at risk, and getting hit pretty much ruins any magic casting.
Different characters have different ranges. The MC, for instance, uses a longsword, while the token healer uses a spear. So, if you wanted, you could have both MC and healer set for Attack mode, and the MC will absorb all of the damage for the healer while the healer uses her superior reach with the spear.
There are about 20 skillsets, and different characters can learn different skillsets. Each skillset also gives you stat bonuses on level up (and sometimes penalty), so if you've already mastered a skillset, you might keep it equipped to get extra attack power when you level up or somesuch.
Oh, and there's this: You have HP, SP, and MP. MP is your main pool of energy, which recovers quickly in combat. SP is your second wind, which you can use if you're out of MP, but it doesn't recover very quickly at all. And if you run out of MP and SP, your skills start costing HP, but do double damage to compensate. This represents a sort of desperation mode, and some characters intentionally have lose SP/MP and high HP. Of course, you can literally kill yourself from overexertion, and healing magic is halved when cast from this state. (All attacks count as skills--so even if you're attacking with a sword, you can get desperation hits in.)
It's still under development, so I haven't been able to test everything in the system. SP might be an unnecessary stat, though in theory, I think it adds an extra dynamic to the system. I've had fun play testing it, though. There are plenty of strategies at your disposal, and the enemies have access to any strategy you have.