My nightmare of a GM was my first time LARPing. The GM was power hungry and basically would railroad everyone with a power trip of unimaginable annoyance. It was like truly stepping into the nightmare world of Vampire the Masquirade (sp) except it was broody and lame. Also to be far that GM had been going through a rough "emo-ish" kind of stage in his life. Now I'm sure LARPing could be awesome, but it sucked so hardcore that I walked away from it forever and felt sad (and a little ashamed) that as a table top RPGer I could actually look down on another group of people.

Your stories?

As for the best experience was actually a Shadowrun where our team took out a heavy JIS naval ship by doing all sorts of fun stuff. Our GM in this aspect is a great story teller and has made every single run we have done interesting and fun. I don't think there was one session where we didn't have fun sitting at his table. He wins my "Best GM award" as it made me feel that this was what everything a table top RPGs should be and finally was. It was like a small frightened child stepping into the light one more time and expecting to be burned again, but only to be bathed in a warm glow of warm glowie...ness.

I made an imperfect call in a Shadowrun game that led to some serious gripe-age from a couple of players. I apologized and attempted to re-jigger things so the results would be a bit more even overall but it wasn't satisfactory. There were thinly-veiled threats of them walking to which I said, "Fine. Go." I put a lot of time into game prep and I won't be railroaded. They stayed and it mostly worked out. To be fair, they were used to the D&D style system where everyone splits treasure fairly and everyone levels up at the same time. They didn't get that some players could earn more karma than others and if they're not in the game that night they could miss out on loot opportunities.

LARPing is one of those things I think needs to be done in a large-scale setting with someone of experience as storyteller. Since it's more acting than strategy-gaming it needs to be with trust worthy people and/or friends you know well. I can see how a bad storyteller could wreck your view of a GM.

Worst GM, a short one and a longer one.

The short one first. Actually, the GM was pretty good overall. But one time he tried to get creative, and created "parchment" from some notebook paper stained with coffee. The paper grocery bag crumpled method (which the rest of us GMs used quite a bit wasn't good enough). Now, the notebook paper did look authentic, but the smell was atrocious and none of us wanted to go near the map. We ended up putting it downstairs for the adventure and sent it home with the GM...

The longer one...same GM, if I recall, when DnD's Ravenloft setting first came out. The GM and one of my friends never got along, so when we all played in this new setting, the GM kept screwing his character. I forget exactly what caused it, but there was some random rolls that happened and my friend's character, who was going to be an honorable, charismatic knight type, ended up with ever-growing white hair (that if cut, would grow back out) and his arms and legs were visibly uneven and different lengths. Pretty much ruined my friend's character and stopped him from gaming with the GM ever again... Whenever there are personal issues that pass into the game world, its just really hard to have any fun!

i don't get tired of complaining about this one GM somehow . .
when he played, he was a rules lawyer, same if he was a GM . . more or less . . because somehow, as soon as we brought up a point he himself had used both as a player and GM that would benefit US for an exchange, he called us ruleslawyers, gamebreakers and a plethora of other things in the same category . . and promptly deklare a house-rule to be in effect that he just made up to close that so called loop-hole to prevent further abusing of the "flaws" in the rules . . and of course, as soon as that particular point was good for him, hey, it did a phoenix and a barrell roll all in one and was promptly ressurected . . and now the joke about it all: he knew shit about the rules for the most part and usually just winged it through role-playing . . i know that at least in my chosen field of expertise i knew more about the rules than he had forgotten by that point . . well, at least he did not know about the chunky salsa rule . . one time he threw several goons with ruger thunderbolts at us and when we declared looting to commence he glossed it over and moved on to the next floor of the building . . and when i actually turned around to get back down to get one or two of those sweet babies, he frigging blew up the stairs below our level . . another time he built a mage that had ONE SPELL on maximum, which was LOWER ATTRIBUTE CHARISMA, because for the first time in months, my character was not the only one with less than 3 points in charisma . . due to me rolling like an adept close combat troll, i managed to actually resist the spell with my 2 points of charisma and managed to kill the mage dead enough to make two new mages dead too . . same run, different weekend, there were MORE Magicians . . one of those actually killed himself, because i got away with Serious Stun after the first Stun-Ball dropped on the group . . on the second casting of the Spell the mage overcasted and botched deadly drain so he just fell down to the ground from the van he stood on and brains started to leak from his cracked skull . . but he had gotten my troll down at least . . same GM, other run, he told me that my STR16 Troll had ost an opposed test to a small flying drone which managed to snatch both heavy pistols out of my characters hands in one pass, after i had hit something with the Savalette Guardian i had bought some hours earlier for about 4500nuyen FOR THE FIRST TIME IN THE WHOLE RUN . .
ok, now that i am home, i will continue:
he had us do a jurassic park type of run . . only with all kinds of para-critters, including swarms of thunderbirds, that giant awakened armadillo thing, hell-hound-packs, i think a group of HMHVV type thingies was in there too . . and after we had spent some in game hours researching the public zoo in central seattle(yes, you read that right, that's still the same park i am talking about), when we try to escape over the main wall, he throws in the gigantic half spheroid magical barrier that's covering the whole zoo . . he did not see fit to mention that one to us while we were doing legwork, nor to us when we participated in a guided toor through the park, where such things should be mentioned, NOT to our mage when he astrally scouted around the general area . . so, basically, he threw us in there to kill a rigger defended with a plethora of drones, several guard-teams with assault-rifles and fully automatic shotguns, let lose all hell upon us by releasing ALL of those critters at once, giving them some kind of intelligence where they did not attack each other but only us, and then basically closed the door on us after having taken the only weapons that had shown some sort of effect(read, savalette guardian with ExEx and ares viper slivergun) . . yeah, we called it quits around some minutes after that, and i did not get back into THAT Train-Wreck . . i have had it with that GM . .

the other time i was badly railroaded was because it was an on the fly run that the GM had laying around pre-done, downloaded from teh intarwebs and my character was the most dangerous one . . so it was not really his fault and i am not blaming him, especially since he actually apologized to me specifically for that and to the group as a whole for that run . .

The answer to both questions, I just look in the mirror....