Well, I never liked the way how light gradients from single light sources (out of terminals or door-borders) where created because it didn't look that realistic, if mappers formed one sector around the other and then adjusted the light. So I played around with new different light-models and well, this is what I have achieved (first time in TNT3):

In screenshot number 1 you see the lightning of two LIGHT3 bars next to one of this nice Quake door-textures heavily used in my TNT series ;) If you now compare this light model to some other versions (this sector-in-sector-one) you will see how much has been improved, because this one looks by far more realistic and cute then all the other ever had (in my eyes at last ;)). This is mostly because the light no more travels around corners, it is seen as a light-beam and behaves in this way! (buildtime 2-3 minutes)

Summary: For sure, you can't use this light-model not everywhere, for example not for floor/ceiling lightsources or light-sources which don't fire the light as one single beam (formulated in a simple way) but further spread the light in every direction. Nevertheless, this alternative model is useful and looks much sharper then other models
Extra-Buildtime: "2-3 minutes" 
Build-Difficulty: "Low"