I started to wonder how many of the words in the dictionary have their .CO taken. So, I started with "A" words and found over 4500. My particular English dictionary is gigantic and has over 109,000 words -- unfortunately many of those words don't make for great domains.
Some that I liked: Alaskans.co Aroma.co Apse.co Azures.co
Have a look for youself. The list of "A" words is here.
Happy Domain Hunting