Here, have a Holy Avenger
Despite the fact that there is perfectly good chart for rolling up treasure in the DMG, this GM will randomly ascribe treasure and gold based on his whims. While this is fun initially, a gross imbalance in the party will ensue, resulting in Hero McUltraequipped and his possee of slightly less-well equipped followers. The DM will gawk in wonder as the party shreds through his BBEGs like they were made of tissue, then will begin throwing higher and higher difficulty enemies against the party, which will ultimately result in a level 10 party dying at the hands of a CR 17 encounter.
No, you can't have a pony. (not for you)
This GM despises all manner of horses with a firey passion of a thousand suns. Whether it's a mule, riding dog, horse, or velociraptor with a saddle, be prepared for every single monster to target it like they were the only edible thing in a thousand miles. If the horse isn't being eaten or shot at, it's running away in the darkness after mysticly untying itself from the hitch.
You want me to do what? heh, it'll cost you.
"Oh, you want those identified? Sure, 300 gold. You need your stats restored? pay me five times the cost, and we'll be copacetic. A potion of Cure light wounds? Heh, do you have a credit card?"
Every service costs FAR more than either the PHB or the DMG indicates it should. apparently, in this world, NPC's are all patterend off the "comic shop guy" from the simpsons, where if you need something, then you must be willing to pay MORE for it.
I find joy in your misery
This GM is all smiles, as long as his party is out of spells, low on hit points, and surrounded by creatures whose CR is 4 levels higher than their combined party level. Nothing ruins his day more than players who want to (ug) roleplay, or "prepare" for the inevitable encounters. If the players come to a town and establish any kind of contacts, he'll kill them off. if they like a magic item, it gets stolen or sundered next combat. Anything to keep the players unhappy.
