I have yet to see any modder besides NTAuthority actually write scripts that alter gameplay.
The G-man's knowledgeable on modding, but he seems to only alter codes in files, and not actually write them (or so he told me in one of his threads, IIRC).
I am going to be taking courses in programming soon enough, so maybe I'll learn how to actually write my own scripts, or hell, even alter the maps.