I'd just got out of the armed forces and had a bit of money stashed away so decided to do the college thing and get an education, this was in March (late 80's), college didn't start till September- I decided to have six months off everything- except D&D.
I co-opted a bunch of kids, mostly younger brothers of guys I went to school with (and gamed with), and every day for... seemingly six months I DM'ed, sometimes 2 or 3 sessions a day. In summer we'd think nothing of starting at 9 AM and going on till midnight- with assorted snack runs. Seven days a week- the guys never got tired of it...
There were two groups of players, AD&D, set in Carse (an old supplement from Midkemia Press), both group were based there and the adventures came thick and fast, but that wasn't it...
By the end of the 6 months we had a Carse Newspaper which the kids had to write stories for (this is pre PC's and computers- or else none of us had a computer)- the paper would come out once a week and the guys didn't know which stories I'd run. It was also 75% about the PCs- Well 'Ard Jim (one of the PCs getting arrested for attacking a man in the street with a 'live cat'- that kind of thing). We incorporated a Blood Bowl League in to the game, we built a stadium in the town (well we drew the plans and did the maths). I'd commentate on the games, and record them on tape- which would then be passed around and/or copied.
PCs died and had memorial services, knew at least 50% of the town's inhabitants by their first names, and for lots of sessions were happy to spend money drinking, getting in to scrapes with the law, and be chased by old ladies with brooms- hardly heroic, but the good stuff if you're 13 years old and are about to snort pop out of your nose.
The players became heroes and horrors and got up to something like 7th level in just six months- I still have all of their character sheets in a big box file, complete with drawings et al.
I think halcyon about covers it...
It gets better, a couple of years later in a bar (where else) a big feller (slightly drunk) comes over to me and asks me if I was... well, me. I'm a big lad so I fess up- yep, I'm me, what's the problem- I thought I was about to get hit. Instead the guy grabs my hand and starts thanking me for teaching his son more in six months than he had got out of whatever years of school. Unbeknown to me the kid wasn't great at reading, writing, maths et al- and didn't give a damn about any of it. Six months later he read at home (mostly fantasy fiction admittedly), his maths up to scratch (GP + XP = get better at maths), and he'd started doing his homework and was winning awards for his 'crazy' stories based on a hell and brimstone Priest called Septimus (named after the kids dead Uncle).
Turned out the slightly drunk guy was his dad, I didn't pay for another drink that night.
As it turned out I went to be a teacher (not at all what I had planned), and the kid went on to do a degree and become the manager of...
I'm not saying I did that- I just gave him a push.
Dungeons and Dragons changes lives, it seems.
That was my best campaign.