A longtime D&D buddy and I finished our first published campaign together called Rise of the Runelords, written for the Pathfinder system (basically D&D 3.75). He was DM, I was a solo PC with a bunch of NPC followers. The campaign went from level 1 to level 16, culminating in an epic battle between my level 16 party against a single level 21 archmage. From what I've gathered, the archmage is the single most powerful character in the entire Pathfinder canon, as no other single monster or character has been published beyond level 20.
Given that its the end game of a campaign that took us a year of real time to play, we went balls out with it: We were playing Dancing Mad from FF6 in the background, describing every action in painstaking detail and epicness, busting out every high level spell, attack, super move, and trick--I was trying to kill that archmage, and my buddy the GM was doing his damndest to go for a total party kill. Gloves were off, Dancing Mad was blaring, and we were just having a ham-fest with it. After all, if your long-ass campaign gets to the final stretch, you damn well better make it as epic as hell!
Anyway, we couldn't kill the archmage toe to toe. So I assigned the strongest NPC follower to chip away at some crystal that served as the archmage's power source. Meanwhile, everyone else and I were keeping the mage busy and trying not to die. So there we were, basically running a stalling strategy, NPC followers dropping left and right, until I was the only one left keeping the mage from TPKing the lot of us...and buying that strong NPC follower just enough time to crack that crystal.
We managed to break it just under the wire, beat the mage, and switched the music to the FF6 ending theme (the 20 minutes long one) for the denoument. I tell ya, when the FF main theme kicked in with its string accompaniment, it really did feel like an accomplishment.