What are some commonly used Latin idioms or phrases?

I am writing speeches for this one character in my fiction. The character is highly educated and he likes to throws in Latin phrases here and there for effect. I know very limited Latin. (res ipsa loquitur, anyone?) Please help.

P.S. Even better would be phrases used in speeches by Cicero, Julius Caesar, and any of the old Roman leaders. Please don’t give me the whole speech, however, as I won’t be able to understand it. Please just include the relevant phrase.