Today I learned something about Forsworn Briarhearts. It took me a while to realise that their name is literal as they actually have a Briar Heart in place of their heart (cue facepalm) which can be observed on one if you remove their armor or if they aren't wearing any. It's where the heart would normally be, of course, and has 4 straps keeping it in place. If you remove it, the model gets corrected accordingly which is a nice touch in a game where ripping the pelt off a bear doesn't leave a disgusting pink lump of bleeding muscle (ala Red Dead Redemption :P).
More fascinating than that however, was finding out that you can pickpocket their hearts. Doing so rips their heart from their body, meaning they die instantly. Which is awesome, considering how difficult they can be. Then again, in most cases it's probably easier to backstab them, but ripping their heart out without them noticing is pretty cool.