15 types of clients, their characteristics and ways to deal with them - Wonderful World of Clients [infographic]. This is a little funny and not meant to be disrespectful. It's a good summary of how to deal well with unreasonable client demands.
Communicating between designer and client (or designer and internal project manager!) can involve odd ways of getting an idea across. Here's a funny cheat sheet for designers. Bright Bold Crap really pops!