Nash, who is already one of the best-known members in the community, once more teases to amaze us. In his development thread over at ZDoom.org he presents one of the most brilliant things I have ever seen done in the Doom engine with clever use of ACS and ZDoom: A real-time day/night/weather system that is highly customizable and flexible as well. Currently it features real-time day and night cycle with tinting across the entire map, sun lens flare, particle clouds in the sky, chance for overcasting, rain and thunderstorms, completely random and in real-time, rain drops that do not fall through ceilings, compatible with sector lighting  (the engine does not overwrite your sector lighting work) and many many more is already in or planned in the upcoming v1.0 of the mod (including the source as well). It's definitely worth checking the thread and praising the programmer.