Never Say Impossible (CSC)

__TOC__
: "My Dwarf fighter, Thuenor, throws his mattock so it lands on top of the wall, steps back, and. with a short run, leaps up to grab the top of the wall. He gets his weapon, dives into the water, and swims to the far shore."
: "Six impossible things before breakfast, eh, Frank? (Sigh.) You sure that he doesn't want to walk on the water instead? OK, I'm gonna need some die rolls."
Players want their characters to do the darndest things. They're heroes, right? Heroes do heroic things. Yet, reality (often in the form of immutable physical or magical laws) has to be considered.
Don't tell a player that he can't do something. If the task is at all possible (even if hideously difficult) allow the character a chance at it, say a 1 in 100 chance for something that's dam near impossible. If the task is impossible, let the player know it by the dice roll he is asked to make. For example, "Go ahead, Frrank, Thuenor needs an unmodified roll of 21 on a d20 to swim with his armor on."
Instead of telling a player his good character can't do something evil (y'know , taking candy from a baby or something equally wrong), let the local authorities teach him the error of his ways. After his character is stockaded, loses most of his possessions, and finds that his Constitution attribute has dropped a point due to that unpleasant disease he contracted in prison, he may think twice before doing evil again.
On the other hand, don't go overboard on the punishment. Make it fair and reasonable (unless, of course, the infracting player already knows that the local authorities are NOT fair and reasonable themselves). Don't kill a character for spitting on the sidewalk (unless, of course, the locals worship sidewalks and he has defiled their god).
The plus side of giving the characters a chance to dice their way out of nigh-impossible situations is that it gives them a chance to get out of situations that would otherwise automatically kill them.