The big hack-and-slash game I wanted to run but never did was my DOOM2/D&D crossover. At the time I thought about it I was playing a lot of DOOM2 and D&D, so it made sense to combine them. They even made DOOM minis at one time, though the only ones I ever picked up were a trio of imps and the cyberdemon. I've thought about painting that cyberdemon, but I gave up mini painting years ago. Too much work. I still paint terrain, but you use a different kind of paint.
What were we talking about? Hack-and-slash. While I tend to zone out during dungeon crawls, I do enjoy a good bloodbath. I was running a high level game (for my group, which means 10th level) a couple of summers ago, and every session was about an hour of build-up, three hours of massive, set-piece combat, and then half an hour of looting and xp. The loose premise of that game was dragonslayers, but they didn't spend that much time on dragons. The best combats from that game were the ones that filled the table. Lots of mooks, lots of different monster types, lots of enemies with different tactics. It took a lot of prep to get combats with that many moving parts, but those were the sessions I most enjoyed running and the ones the players seemed to have the most fun at as well.
The other great thing about a short-term, mini-series style game is there's no need to be stingy with anything. Have everybody make two or three back-up characters and throw CR's out the window. "Recommended Wealth by Level?" Screw that, bad guys should be like pinatas, exploding with loot. You want to give a 5th level Paladin a Holy Avenger, put an artifact in every dungeon, steal Vecna's other eye, whatever. You don't have to worry about wrecking the game, because you're only in it for a few months anayway. You can always start over later and be sane. For now, go crazy. No crafting rolls, no boring scenes. High magic, high risk, high reward, hi-octane. Full-tilt boogie.