It can be more, but for me it’s usually just one person who doesn’t move when the game starts in war games. Then when they do they get mad at the person cough me for punching them/grenading them lol.
You shouldn’t attack people who don’t move, unless they have one kill, or they really don’t move.
Sometimes I’m busy with party chat, invites, text messages, and other stuff.
When I see someone standing still, I just ignore them cuz it’s likely they’re occupied with something.
I’ll never attack someone afk at the very start of a game - I’m too busy sprinting in to catch the opponents off guard (plus if someone is busy for the first minute or so of the game then fair enough IMO). I might give someone a nudge later on in the game just so their controller vibrates drawing their attention - I haven’t even done that in some time though.
Yes sometimes RL gets in the way of playing, like taking a quick convenience break, that you just dont get to return in time before the game starts.
People who are static the whole game I believe are booted from the party at the end.
I did once sticky det one of those players, as I noticed the opp team were specifically looking for him when he re-spawned to assassinate him; got a ‘showstopper’ and a team that thought twice about doing it again 
I leave teammates alone when they AFK but for some reason I have to go for the enemies when they AFK. I know they don’t want to be away from the game and I should leave them alone but it just comes to me, easy kill= easy win, I have left some of them alone and one time in Halo: Reach one guy shot at me then noticed I was AFK and left me alone. That was the only time someone did not kill someone AFKing in the same match I was in.
I had an epic momment last night with a couple of AFKs.
The match started on Complex. I jet packed up to grab the rockets then killed 2 moving players with the first clip. I reloaded while slowly jet packing down and aimed at a player coming out of a building. I saw 2 AFKs behind him by the back wall. I shot one rocket past him to nail the 2 AFKs on the back wall while dodging his BR shots and managed to hit him with my second rocket before my feet hit the ground for a triple kill. It was my most epic and skillfull cheap shot ever, lol. For a moment it felt like Firefight Arcade.
Funny when they are like this on the opposite team. Played an IS game the other day where most the other team quit leaving only a guy like this and I just assassinated him until the timer ran out.
Start of game is okay IMO- maybe they’re on the way back from the fridge or checking emails.
I often play with the sound off and sometimes I’ll get distracted while waiting for a game and won’t realize it started until my controller vibrates. So that punch is a good thing.!
After a few minutes of inactivity I take umbrage. And if we’re getting schooled by the opposition then I’ll sometimes submit a player review for unsportsmanlike conduct.
Oh so the punching vibrates their controller? Good then! I always feel like I’m wasting my time.