Ultima was already used, way back on page 2 of the thread, and Tonberry was already used back on page 4. What's funny, is that even then, Tonberry was used to cover up Tiamat, which had been posted twice.

All you have to do is quickly scroll through the thread, and go to the previous posts of the letter you are about to post, and make sure you don't post a word that has already been used.

How about:
T - Twin Lance
U - Ulysses