Q:

What does "though" mean in these sentences? 

I knew these are American English sentences, and they are informal.  However, I would like to know what exactly it means, or it simply means nothing, and people merely want to add something unnecessary at the end of a sentence, because it sounds fetch. 
Sentences like:

His denim jacket, though. 
I love the way he talks, though. 
For real, though. 
Really, though. 
What's up though
When are you coming over, though? 

A:

1 incomplete sentence
2-6 It implies a contrast.  
"He's a bit of an idiot.  I love the way he walks, though." 
EDIT:
I've recently heard phrases like the OP's #1 His denim jacket, though
It's slang, but the best way I could put logic to it is that it implies that one could notice a lot of things about this person, but the jacket supersedes all other noticeable traits. ( Thus, the comparison) It can be used as a compliment or put-down. 
Those shoes thoough! ( A ragged pair of sneakers or a fancy pair of snake skin business shoes.)   
This goes along with @Edwin Ashworth's comment.