Dying is almost always a bad thing in TF2 (indeed, most shooters). You aren’t helping your team while dead, you aren’t having fun while dead, and a good many unlocks are dedicated to keeping the player or his teammates alive. Trying not to die is, for the most part, a pretty good strategy and you’ll go far with it.
So why would you ever want to die? And I don’t mean “Divebomb the enemy medic, caber them, and then who cares if the enemy mows you down”, I’m talking “bind a key to ‘explode’ then press it and explode for no reason.” Here are a few situations:
1. In case you get stuck. Tf2 is not a perfect game, thank god. There are plenty of ways to get stuck on, in, and under things, and sometimes death is the only way out. May seem obvious but true. Sometimes you’re not even stuck, but the form of death is long and inescapable. A great example would be the bottomless pits of death in koth_lakeside_event and plr_hightower_event. Just gib yourself as soon as you fall in and shave an extra 10 seconds off respawn.
2. Give an Engineer metal at the beginning of the match. In many competitive Highlander matches, you’ll see defensive soldiers, pyros and scouts running up to the Engineer before the round starts and suiciding. They’re doing this because the dropped weapon will give the Engineer 100 metal, which helps him get all his buildings up quicker. And it’s not like the soldier and scout have anything to do before the round starts, plus they have the speed to be back in position before the gates open.
3. Deny “on kill” effects. I have totally gibbed myself rather than give a Zatoichi wielder the rights to his other weapons, an Ubersaw Medic 25% Uber, and other examples. Occasionally you know a fight is about to go south; you don’t have any shots loaded, you don’t have the turning speed to meet your foe head-on, or your death is an acceptable trade to deny even the chance of your opponent gaining the benefit. The Medic in this video gives away 75% Ubercharge when he didn’t have to.
4. Ultiduo. I briefly went over this in the Ultiduo article I wrote, but if you plan on playing Ultiduo you need a key bound to suicide, especially as Medic. Ultiduo is all about Uber advantage and positioning, and the spawns do not allow the players to reenter. For that reason, if one team’s soldier dies the Medic often suicides as well. It’s just not worth remaining out in the main area without your soldier unless the situation seems oddly favorable (such as the enemy soldier also being dead). You won’t be dealing any meaningful damage against a combo, and the enemy is going to wait until the last possible moment to kill you so that you lose the maximum amount of Ubercharging time. They may even fight to keep your soldier away from you when he does respawn, for the same reason. Far more efficient to just die, respawn with your soldier, and try it again.
I didn’t have a key bound to suicide for the longest time, because I thought, “I’m not playing this game to die, I’m playing it to be a credit to team.” It took a while before I realized you sometimes could do both.