Today I handled an interesting balance issue: a player tried to use 'Grease' combined with 'Fire Arrow' to create a permanent burning zone in a narrow corridor, which would have ruined the tactical design of the entire area. After some thought, I decided to allow the action, but let the smoke trigger a chain reaction in the overhead ventilation system, blanketing the whole area in thick smoke. Rules are the skeleton, but creativity is the flesh and blood that makes the world breathe. Fellow GMs, how do you handle players' 'rule-bending' creativity that goes beyond expectations?