Almost as long as games have been around, players have been looking for ways to complete them in unusual ways. Oftentimes, this results in pacifist runs - playthroughs in which no NPCs are harmed or, at the very least, killed by the player in the duration of the game. The Metal Gear Solid series in particular has adapted over time to allow more room for players to focus on this style of gameplay, and has arguably become more interesting gameplay-wise as a result.
The Metal Gear Solid (MGS) franchise didn't necessarily start out as incredibly focused on nonlethal gameplay. While it was occasionally possible in early games, most boss fights could not be resolved in a nonviolent way, and even when they could there were usually scripted kills that players couldn't avoid. As the series progressed, however, so did its available styles of gameplay. By the third game, all boss fights could be completed without any kills. The fourth and fifth MGS titles also included achievements for clearing areas nonlethally, and items like tranquilizer darts became features that players could use to progress in a pacifist playthrough.
Other action titles followed suit. Dishonored, a highly praised stealth title, includes unique gameplay opportunities for players who choose to progress through missions nonviolently. Some games in the Thief series function similarly. Mirror's Edge, while often requiring hand-to-hand combat, allows players to go without using actual weapons to inflict fatalities on any enemies. Indie games also made use of the feature. One-third of this year's E3 games were nonviolent. Undertale, an indie title that became highly influential following its release back in 2015, even featured a pacifist route that required players to go without killing a single character in the game.
Why More Games Should Follow In Metal Gear Solid's Footsteps
Allowing for non-violent resolutions within a game creates more opportunities for player freedom. Fallout: New Vegas is widely considered to be one of the strongest entries in the Fallout series, and one large reason for this is because of how much room players have to make creative decisions. With high enough charisma, luck, and other skills, players can progress through every confrontation in the game in a nonviolent manner, crafting a protagonist who relies more on diplomacy than proficiency with weapons. This is a great way to allow for more replayability in a game, increasing its longevity.
Skyrim has experienced a similar phenomenon, as players often let players resolve things nonviolently, and more games should allow room for such diverse playstyles to blossom.