When I play heavy I love seeing black box soldiers, since if I run into one at midrange and I actually manage to have reasonable accuracy, they either need to be 100% accurate or use one of their rockets to run away. Otherwise, if I can manage to absorb/dodge/lessen the damage of at least one rocket, I eat the other two and they reload (i.e. they are dead).
Of course, this is because most soldiers fortunately don't seem to use the shotgun. It's like shotgun pyros. Those things are so annoying. You're all, I'm out of range of this pyro, and the pyro is all, click click bullets, click click bullets.