Yet another. Two badguys; number one approaches from 11 o'clock, attempts to engage you in conversation, asks for a cigarette light or something else. Number two comes from 6 o'clock and 1) grabs you around the neck, or 2) a bear hug around both upper arms.
Now, there are plenty of what ifs from here. But in 1) when number one actively joins in you can, if having reasonable belief that number one is number one in a two man assault - shoot number one. If he suddenly draws a knife and says give me your wallet, now you know he is number one - and you can still shoot him.
Say number one's eyes bulge, he drops the knife as soon as he sees a pistol coming out, turns and runs. Number two doesn't even know you have a pistol in one hand unless he was looking down over the front of your body and saw you draw it out. If you reasonably believe you are losing a life and death fight with one man - in this case you can stick the muzzle in his belly if he is right up against you, and shoot him. If he has you drawn over backwards you, you should be able to draw, and orientate the muzzle and bore axis with his upper body quite easily.
In the case of the bear hug, depending on position and type of holster and grip, the type of handgun (length of the draw required to clear the holster) you still might be able to draw - something you could not do with a strongside. Again, number two may not be aware you are armed until it goes bang. In any case, the first time it does, number two is quite likely to let go and run like a scalded cat. As soon as he lets go, shoves you to the ground, or changes his tactics - you are ready to shoot him if it is neccessary.