Years ago, I never used my signal. At some point, I changed that viewpoint drastically and now make every attempt to do so. Also, like someone else mentioned, I get pissed when other people don't - especially in those instances when others are particularly dependent upon a signal (e.g., you're waiting to turn right, there's a car coming from your left and you're waiting for them to pass, only to have them turn right without a signal, thereby juking you).