I think anyone who's been running games for any length of time must have one or two of these old chestnuts stashed away in his dice-box-shaped hope chest: those campaigns that almost got off the ground but fizzled before they had a chance to reach their full potential.
In a way, I find these "almost-rans" even more irritating than the "campaigns I wish I could run but probably never will" sorts. At least with the latter, there's always the fantasy; "Maybe someday...," you muse, drumming your fingers thoughtfully on your chin.
But those almost-rans? They had their shot and they failed. Your best bet is that perhaps some day in the distant future you'll have a chance to sit down with a different group and try again, but in the meantime all you can do is bitch about it on the Internet and ask for commentors to commiserate and share their own almost-rans. See what I did there?
My only extended break from regular gaming occurred between late 2000 and early 2003. A fairly tumultuous time in my life, fair to say, and my return to gaming also signaled a return to a more settled, satisfied life in general. To celebrate, I put together an awesome campaign (if I must say so myself).
I made up 12 PCs for GURPS (an impressive feat in itself!). Each PC was represented by a senior photo taken from my high school alumni web page. Class of '84 (which was not my own graduating class, for those of you keeping score at home). I made up a contact sheet with all the photos on a single page. Players chose their character solely on the photos, then got the character sheet handed to them. The campaign kicked off on December 2nd, 1983.
Half the PCs were nerds and dweebs, the other half were jocks and cheerleaders. One of the nerds was the brother of a cheerleader. The jocks had gathered at the cheerleader's house to watch the MTV premiere of Michael Jackson's "Thriller" video; the dweebs had gathered in the basement to play AD&D.
The idea was that, in this alternate setting, the Thriller video was actually a mass raise dead spell beamed out across the world, bringing forth hordes of zombies (whose only weakness was dance music, naturally--unfortunately the campaign ended before the PCs discovered this). We had a blast with the first session, RPing some conflict between the jocks upstairs and nerds downstairs, then having a disturbing encounter with a zombified roadkill cat, and ending off with the first wave of zombies attacking.
For whatever reason, things never progressed from there. I can't really remember why now, seven years later. It's a damn shame, though. For one thing, having all those pregen PCs made the inevitable casualties no problem; if someone bit the dust, you just handed them a new character sheet. I think we had three casualties in the first session, including a nerd who blew up a gas station (and himself) in a heroic last stand.
Also, in addition to dancing zombies, once the shit really started hitting the fan I was going to introduce The Misfits (sans Danzig, who naturally would have become a local zombie lord) as professional zombie hunters (the campaign was set in New Jersey). That would've been sweet. I hadn't made up my mind yet whether Michael Jackson, Vincent Price, or John Landis was the master necromancer and main villain, though. Whoever it was, they'd be based out of L.A. and the campaign would follow the group as they fought they way across Zombie America to get to the master necromancer and kill his ass.
Ah well. Maybe I'll get another chance with a fresh group someday...