I recently heard of a MMOFPS which sounds pretty awesome. No grinding, and huge, large scale battles that make it feel less like paintball matches, and more like you are a soldier in war. Uses a similar system to Frontlines, where capturing objectives changes the frontline's position in the battle, yet it is also flexible to the amount of troops moving. You push through the line, the line will move. You flank, it'll shift. I thought it sounded kewl, and seemed like a change in the monotony of MMORPGs.
I'd just recommend finding some good Battlefield 2142 servers if you want the large-scale battle feel... 48/64 players is plenty, and lag isn't an issue like it was for PlanetSide.
I'd recommend giving Sword of the New World a shot if you want to kill some time mindlessly grinding. It's quite a bit like Dungeon Siege, and the translation errors are funny. The art style's kinda fun... stanard Japanese anime-style crap (like Final Fantasy) meets Renaissance/Exploration era. Fun stuff.
It's a pure grindfest, but it was fun enough that a friend and I burned about 30 hours on it over the course of a couple weeks, and you can't beat the price

MapleStory... a friend blackmailed me into playing it with her one day, and even SHE was disgusted with it after 20 minutes.