Variations on penalties

[blargney the second]

The http://www.enworld.org/forum/general-rpg-discussion/324158-you-can-but-penatly-same-you-cant.html thread got me thinking about the types of penalties DMs can impose in d20 games. Naturally, circumstance penalties and AoOs spring to mind, but there have to be other interesting options as well.

I'm interested in examples of both existing, written rules well as neato house rules of circumstantial penalties/punishments for inadvisable actions.
-blarg

 

[blargney the second]

I'll go first.

1) "Sure, you can try to intimidate the city guard. He's got some allies nearby so you'll take -1 per guard and if you fail by more than 5 something bad will happen." (ie thrown in jail)