Goodreads.com: gr
http://www.goodreads.com/search?query={query}
Kickass Torrents: ka
https://kat.cr/usearch/{query}
I also duplicate a couple of built in searches just because I don't like the keyword. For example, I'm too lazy to type Amazon so I built one that uses "amaz". Same for wx instead of "weather". Mostly I do this because I've used these same keywords for search in Firefox for years. Old habits were hard to break.