Hero classes' unique equipment

[Yvain]

There is no such possibility And If there is a situation like you mentioned, only one zwei has nothing to do. Generally there should be even moar zweis than RGs...

Nothing to do ? Damn, you have not understood what are hero class... Royal guards are better at shielding, and zweihanders are slightly better at slashing. But they are still good commandos with at least 8 in shield and 8 in power strike. Every commando hero class is interesting and will always be useful near the shieldwall... Pikemen just have to check if any commando needs a place to slash, since they usually have shorter slashing weapons.
Sharpshooter hero classes ? Chosen Marksman if you really like crossbows, Pavise Champion is an excellent choice if you like flexibility. Aventurier if something interesting for them is coming in next patch

[Winter]

Well, some interesting responses here.  Once I finish getting all of the hero classes, I should write a guide with recommended equipment, strategies, usefulness, and goodies like that.

In response to the original question, the Chosen Marksman class is great for crossbowmen that do not already have legendaries, as it gives access to the very impressive Big Shot and Eastern Repeater.  You can also get the Elegant Crossbow instead if you are a little on the poorer side.  For Commandos, the most stereotypical answer would be Zweihander or Royal Guard, since Legionnaire isn't very useful unless you already have good throwables for him, especially the Very Heavy Throwing Axes since those can be double stacked in your inventory in the place of your one hand weapon so that in the end you are bringing a shield, two stacks of axes, and a fun support item.  However, if such things are not available (Craftable Throwing Spears also work great), I would generally suggest Royal Guard if you are usually one of the only few Commandos on the server, Zweihander if they are usually crowded for you.  Obviously Royal Guards can still slash and Zweihanders can still shield pretty well.  It isn't like they lose stats by going  hero like SOME people seem to think.  It is all your choice, have fun

[Shagz]

People have opinions, People throw numbers around to make something appear more important than it is. (Please refer to the native guide, then apply percentages before opinions get flung around)

Research what you would like to do for either class, ask player opinions, weigh up pros and cons.

As winter mentioned just have fun.