Pyro, heavy, or spy?
Edit: Popular opinion is spy, so I'll bring some counterpoints:
In pubs, I've found spy to be more effective than heavy. Pubs are bad at finding cloaked spies but are actually decent at headshotting/focusing heavies.
In 6s spy can occasionally be better suited to making a pick than a sniper.
Pyro and heavy are only useful for defending last, while engi and sniper are also useful for this.
So, what's the least useful class now?
Edit: Popular opinion is spy, so I'll bring some counterpoints:
In pubs, I've found spy to be more effective than heavy. Pubs are bad at finding cloaked spies but are actually decent at headshotting/focusing heavies.
In 6s spy can occasionally be better suited to making a pick than a sniper.
Pyro and heavy are only useful for defending last, while engi and sniper are also useful for this.