The one that's been driving me crazy lately: 4 as a synonym for "for." I understand some percent of the population "rites lik dis 4 serch" -- but I certainly don't! When 4 = for, and "for" is on every page on the internet, it almost had me pulling my hair out.
Here's an example (but not my exact query). "iPhone 4" will match pages with "iPhone" and "for."
Here's an example (but not my exact query). "iPhone 4" will match pages with "iPhone" and "for."
http://i.imgur.com/vN1oh.png