Subverted or not? Too soon to tell; the clearest Word of God actually states that Joss and the cast and crew want Felicia Day back for the sequel in any capacity; her revival as Penny is neither guaranteed nor ruled out.
Invoked in the "Heist" episodes of Achievement Hunter's Let's Play Grand Theft AutoV series. Once a heist has officially started, if any member of the Fake AH Crew gets killed, he does not get to continue on with the Heist and gets no payment. This is further set up by having the crew member's audio muted and the footage focused on the remaining crew members for the remainder of the Heist.
In Pyrrhic so far Chase Traviss, Zelda Swift, Tina King, Sonny Chance, Xenia Daugman, Tom Tucker, and Benjamin Rogers have died. Being that this is inspired by Battle Royale, it's likely the list will continue to grow.
Donut is shot in the end of Red vs. Blue: Recreation (Season 7) and is pronounced dead by Doc in the beginning of Revelation (Season 8).
Still no confirmation on whether Tex, Sister, and Lopez are really gone for good, though.
Tex in fact fell victim to this twice: the first Tex died along with Alpha-Church when the EMP surged, and the Tex that returned in Revelation was "forgotten" by Epsilon-Church at the end of Season 9 and erased from existence.
Survival of the Fittest: Everybody except the winners of the game and Burton Harris, due to some Body Double antics in Burton's case. He ends up dying anyway. Also. some handlers are fond of putting fake 'Student deceased' messages in their posts when it seems as if the characters have died but are actually alive. (very uncommon though, and it's invariably revealed to not be the case). Also: Maxie Dasai To escape in V3