Banning: Is it ever a good idea? If so, what do you declare off limits?
House Rules: What balances gameplay without players getting upset?
Optional Rules: Should flaws be allowed?
Deoptimisation: What advice would you give for bringing a campaign into line, when it has come a bit out of control without making players feel nerfed?
General DM Advice: Anything and everything else.
Anecdotes: A sort of What's a DM to do for the Optimising crowd. Or, indeed, just your war stories.
Banning: Spells like shapechange, time stop, disjunction, wish, polymorph.
House Rules: Mostly buffs, like spot + listen = perception, move silently + hide = stealth, etc. So i guess they don't mind.
Optional Rules: I don't have a problem with flaws, but i will make the player sorry for his choice at least once in the campaign
Deoptimisation: If the players can kill anything they encounter, just change the enemy tactics. Like, throw a political plot in your campaign, where the top enemy cannot or should not be killed.
General DM Advice: If your players like to hone their optimization skills, spice up the character creation. Select 5-6 books which will be your "extended core" sources (probably PHB, DMG, MM1, XPH, UA, main campaign sourcebook) and then draft a number of books from the rest that are going to be allowed.
Anecdotes: We were playing in a "real world" campaign, roman era. So we are walking in a desert (we're like 5-6 level) and we encounter 3 wizards. They are not hostile, so we just talk, but one player announces that he is going to charge one of them for no apparent reason. By some twisted turn of fate we manage to kill them all (they were 15 level+). The DM is then fed up and he keeps saying that now we cannot finish the story. Turns out, those 3 wizards were
the three wizards that followed the star to baby jesus
. To finish the story we dressed up with their clothing (actually, we were a cleric, a ranger and fighter) and brought the gifts to baby jesus ourselves
. Bottom line, only kill wizards when they are alone.