See Heretic II for examples.
Fireball effect should just highlight certain polys as it flies by. On the G200, it paints blacked out portions, and on the G400, it's the same in indirect and produces spectacular technicolor effects in direct.
There are other notable examples (incl. some occasional lighing screw-ups on the screen- poly's having light on them when they should really be in shadow, etc.) within this app.