The description of the druid's Wild Shape feature says:
Starting at 2nd level, you can use your action to magically assume the shape of a beast that you have seen before. […]
- You choose whether your equipment falls to the ground in your space, merges into your new form, or is worn by it. Worn equipment functions as normal, but the GM decides whether it is practical for the new form to wear a piece of equipment. Your equipment doesn't change to match the new form, and any equipment that the new form can't wear must either fall to the ground or merge with it. Equipment that merges with the form has no effect until you leave the form.
For the sake of this question, let's assume that the GM decides that "practical" means a roughly humanoid shape. Or in other words, it can (at least occasionally) walk on two legs.
We can also assume that the Druid is wearing studded leather armor (12 + Dex modifier).
It is also worth noting that some creatures have natural armor, and natural armor doesn't stack with actual armor.
The druid is a Circle of the Moon druid (PHB, p. 69), which gets the Circle Forms feature (it increases the CR limit on what the druid can Wild Shape into):
The rites of your circle grant you the ability to transform into more dangerous animal forms. Starting at 2nd level, you can use your Wild Shape to transform into a beast with a challenge rating as high as 1 (you ignore the Max. CR column of the Beast Shapes table, but must abide by the other limitations there).
Starting at 6th level, you can transform into a beast with a challenge rating as high as your druid level divided by 3, rounded down.
What Wild Shape creature(s) would actually benefit from the Druid's existing armor? (I’m not interested in getting barding.)