Another falling stunt you see a lot in any action shows is where the hero jumps down from a higher level onto the bad guys. Watch the guys being jumped on, and they're actually catching the guy to help break the fall. Instead of stepping back and letting him faceplant the floor like real bad guys would. The stunt guys really deserve their own Oscar and Emmy categories, it's tough work.
Shatner should recieve more credit himself, as he performed some great stunts on TOS; someone already mentioned the fall in "Journey to Babel,"
but another notable stunt was the close up of his leap/kick over the med table in "Mirror, Mirror"
and the fights with Tracey (both) and Cloud William in "The Omega Glory."
It really paid off when Shatner was cleary involved.
Props to 42 year old Morgan Woodward too for The Omega Glory.