I think you’re going to have to be more specific than that. It’s not possible that you always get killed in 1 shot with any gun hitting you at any point in your body in any source game.
In Counter Strike, it has to be a headshot to be a 1-hit kill, unless you’re already low on health, in which case it’s not really a 1 hit kill. I think maybe an AWP could bodyshot you in 1 hit also, but most guns will take a number of hits to kill you.
In TF2, there are only a few things that can 1 hit you, such as a sniper headshot, a spy’s backstab, a sticky bomb trap, crit rockets, etc. Generally it’s easier to stay alive in TF2 than other FPS games.
Haven’t played DoD, so can’t comment on that. But it sounds to me that other people can just aim better and take you out with headshots before you can kill them with bodyshots. It’s also very likely, since you’re playing gungame, that several people are shooting you at once, so it just seems like you’re getting 1 hit killed with bodyshots, when you actually take a lot of damage from several sources at once.