Olaf the Stout said:
My first thought was "jerk" (actually my first thought was not grandma friendly enough to post).
If you are going to come up with house rules for D&D at least have the decency to let your players know about them before they come up. Some rules changes things that much that they can influence players combat actions, character class choices, feat selections, etc.
How would you feel if you had spent hours coming up with a character specialised in two-weapon fighting, only to find out halfway through the first fight that the GM had changed the rules so that the concept wasn't remotely useful any more? I wouldn't be too pleased to say the least.
I give all new players a hard copy of the house rules before they roll up their character. I also let my players know that my house rules aren't set in stone and that if they have an issue with any of them or would like to change something I am open to discussion.
Olaf the Stout
I heartily agree any HR should be spelled out ahead of time. I'll take it one step further - I think DMs should tell the players what books they may draw feats, classes, spells, and magic items out of. Personally, I name the books and exactly what PrCs, base classes, spells, and feats are allowed from those books.
But in my experience, it still really doesn't matter. Players rearely pay attention to any of this.
I am running a game now. Before we began game, I poured through all the books I was going to let PCs pull from - PHB, Complete Arcane, Adv, Wr, and Div - and made a spreadsheet of every available feat and class I was allowing. Since magic works a bit differently, I wrote up a brief magic explanation and went to the trouble of making a spreadsheet of every player-available spell from all five sources. I made it sortable by school, subschool, type, spell level, class spell list, and spell name.
I posted all of these documents to a website, emailed out the URL, printed this out in a campaign primer along with any HR, and handed it out to the players two weeks before game began.
We used it extensively during character creation.
And yet, despite all this work, players will come to game with their levelled up character with a feat or spell that is not one the allowed list. Invariably, I will call them on it and they will say "Well, why isn't it allowed and how was I supposed to know it wasn't?"
Then, in what has become a famous answer, I wordlessly pull out my primer and hold it up, walk it over to him, open it as if he were a five year old, point to the feat/spell list and ask him if he sees it on there.
He did this three sessions in a row (well not in a row, but three sessions in a row that were sessions in which the PCs brought levelled up characters to game). I know what he is doing when he levels..he is just going through the books and saying "OO..that looks cool and beneficial!", writes it down and never checks to see if it is allowed.
So yes, DMs that don't share their HR or allowed material are not being very good DMs. But players that don't use the material they are given are a big problem too.