Caleb's first word at around ten months was "Amen." He said it often and with great emphasis, sometimes at appropriate moments (like before a meal) and sometimes at inappropriate ones (like when I was talking with friends and he wanted to put an end to the conversation). In any case, it was a good first word, one we could be proud of.
Nathan's first word is "cool," as in "Whoa, that car is way cool." I'm blaming it on his older brother.