I've had this idea in my head for quite some time, using DECALDEF to create cool animations on the walls. You could create groovy disco lights, team-icons for CTF bases, projectors etc. using animated decals. I've never seen it done before though so I thought I would submit this to FX as an example (which is useful in its own right for maps)
Submitted: CaptainManiac Sprites: BadMojo ACS: CaptainManiac,BadMojo Idea by: CaptainManiac Special Thanks: Blue Shadow,MaxED,Scifista42,Buuu342 Ideabase: The Fading and Blood on Screen effect from The Saboteur's regeneration system
Enables blood splatter effects when suffering damage and/or dying. Intensity of the damage splats are proportional to damage suffered. Also provides "fade" effects for when the player's health gets below 50%. Effects can be individually turned on/off or modified.