Suicide runs are an opportunist tactic mainly used as a method of last resort. It requires quick thinking and can annoy enemies for not getting their XP.
Suicide can happen in one of two ways. Number one is the defence, in which you are about to be killed, but to not give the enemies the points from your death, you throw a grenade that kills yourself. Then there's the offense, in which you are close to the enemy but not close enough to knife and you can't aim your gun fast enough, so you chuck a grenade, or by running up to a group and letting lose a grenade, instead of killing one before the others notice you and kill you. It's a simple tactic that has it's advantages and disadvantages and can be impractcle, and will generally require quick reactions to complete.
• Stops enemies from getting XP.
• Annoys enemies.
• Can get you quick XP.
• Sometimes you will get the "close one" XP award now and again.
• Faster kills
• Killing yourself will take away your number of kills by 1, meaning you have to take 2 with you to improve your kill total by 1.
• Will get haters sometimes if you do it too much
• Will be deadly if fought before killing move.
• Enemies might guess your tactic after a while, causing you to be shot before a suiside run.
• It will cause your death total to go up, making your K/D ratio, so make sure you don't care much about that.