Is "Am" instead of "I am" proper slang?

I tried to coax google into finding results for "am not preceded by I", but failed.

Now my question is: Is saying "Am" instead of "I am" valid slang?

Examples:

• Am a God. Obey.


• Am driving. Can't talk now.



• Am a cat. Food plz.

By "grammatically correct slang", I mean if it's okay to use such sentences when talking, writing signs, registering domains, et al, when the intention is to not be serious, i.e. will native speakers understand?