Which shields can be used by a ranger or a sentinel?

[ThePeter]

For sure every class has its benefit yet for normal runs the warden is obviously the best choice.
The other two classes are probably better for kiting and runs with just a few people but the fact that i can't use a shield on these classes makes them far less attractive in my opinion.
It probably happens one in a thousand times that you grab a shield and have actual use of the bonus shield skill.