|Broken Arrow (1950) [Ben Slade]: Stabbed in the chest when Jeff Chandler throws a knife at him, after Will and his men ambush Jeff, James Stewart, and Debra Paget. Will's body falls into the river below immediately afterwards.
The Kid from Texas (Texas Kid, Outlaw) (1950) [O'Fallon]: Fatally injured in a battle with the posse; he dies shortly after shooting Albert Dekker. (Thanks to Brian)
Bandolero! (1968) [Pop Chaney]: Shot to death by Rudy Diaz' bandits when Will reaches for a moneybag during the big shoot-out. (Thanks to Brian)
The Waltons: The Empty Nest (1978) [Zebulon 'Grandpa' Walton]: Dies (off-screen) of old age/natural causes, before the episode begins. (I haven't seen this episode myself, but the character's death was written into the show after Will's death in real life.)