Currently use this to weed between pavers and stones.  Any ideas what it is?

I Believe it is a windshield cut out tool...

Edit: Or was it for door panels?
I have 3 of them, I have never used any of them for anything ;P

It is what you are using it for....

This one by Burgon & Ball (Sheffield, UK)

another in use

Hmmm....

Perhaps that is why it never worked on windshields ;P

It looks like an angliced version of the Indian 'kirpi'

 

Pity the dandelion that meets that thing ;P