This is nothing to LOL about!
Depends on the game. If the game allows one to go through it without killing anyone (Metal Gear Solid, Deus Ex, Dishonored) then that's probably how I'll end up playing it. Generally, if a game has stealth options then I'll take advantage of them.
If it's some type of FPS online then I usually won't particularly care- unless it's Story Mode, in which case it's situational. Though, there are some games where I do stealth depending on the mode.