1.) The stuff that really gets on your nerves, the type of people, places or events that you just absolutely hate.
2.) Obviously another word for poop.
3.) Stuff that is bad ass, a universal word that can be used in any situation. Inflection and preface conversation clearly defines the word.
If a hot woman/man walks by, you can say:

Man, that bitch is the shizank!

Clearly a positive comment.

If an ugly woman/man walks by, you can say:

Damn, that (chick/dude) looks like shizank!

Clearly a negative comment.
Get the shizank mug.