mine is undoubtedly Ignus from Planescape: Torment.
A pyromaniacal mage, Ignus is chaotic and insane. Ignus once attempted to burn down the Hive, and was only stopped by a collaboration of many local magic users, from minor hedge wizards to mighty sorcerers. Furious at his mad killing spree, they converted him into a living conduit to the Elemental Plane of Fire as an ironic punishment. Such treatment would have instantly incinerated a normal mortal, but Ignus survived. Stuck in a semi-coma and reveling in the never-ending flames coursing over his body, he was eventually made into a mascot for the Smoldering Corpse Bar.