What are some famous Black Hat SEO techniques?

Unrelated Keywords. ...
Keyword Stacking and Keyword Stuffing. ...
Tiny Text, Hidden Text, and Hidden Links. ...
Cloaking. ...
Doorway Pages or Gateway Pages. ...
Bait-and-Switch or Page Swapping. ...
Duplicate Content or Mirror Site. ...
Spam Blogs or Splogs.

- Duplicate content
- Keyword stuffing
- SEO cloaking
- Hidden text and links
- URL masking

Keyword Stuffing.
Reporting a Competitor (or Negative SEO)
Sneaky Redirects.
Cloaking.
Link Schemes.