1. White text on a white background (I know what you're thinking, but black on black won't work either.)
2. Hidden text over an image
3. Hiding text with CSS
4. Linking/keywording in tiny text (font size '0' doesn't work either, smarty pants)
5. Linking from a hyphen, period, comma, or any other little character.
6. Use the Meta Keywords tag. This is a giant waste of time.
7. Use your Title Tag as a place to list keywords.
8. Fill up your Meta Description with keywords, forgetting about click-through rates
9. Name your images with the character limit in keywords
10. List every city and zip code within a 10 hour drive
11. Put 2000 words of keyword rich content below the footer
12. Keep track of your keyword density (Thankfully, I've heard a lot less from eager website owners on this topic in 2010 than I did in 2009.)
14. Reciprocal Linking
15. Link Farms
16. Link Wheel
17. Link Exchange (unless it is a real and substantial business partnership or relationship)
18. Three Way Linking (or Two-way, Four-way or any other way)
19. Forum/comment spam (thanks Rob)
20. Submit to thousands of directories for $12.42.
21. Segment your content and launch sub-domains so you can link to yourself
22. Try to get the search engines to index all of the search result pages on your site.
23. Publish a new page for every single keyword target.
24. Place location keywords in your places page categories.
25. Create a bunch of Google Places pages that all list the same physical address.
26. Torment your customers so you'll get plenty of (negative) reviews. (this one got a lot of attention late last year)
27. Provide different keyword rich business names to local sites.
28. Measure your website's strength or success with PageRank.
29. Find out which pages are ranking well and never touch them again.
30. Blindly target keywords just because your competitors are.
31. Submit to hundreds of search engines automatically for $9.99.
32. Use robots.txt to control robot access (I've harped on this before)