My "favorite" as in, most favored or most preferred is communication in person or via IRC.
I don't like email for casual conversations or discussions, as it's too much of a "one way" median rather than a 2 way method like IRC or talking in person (or instant messaging.)
I like IRC because it allows me to do everything on a PC without touching a mouse. (I don't like Instant messengers, because you have to use the mouse generally if you are involved in multiple discussions at the same time, in IRC on BitchX, I can easily keep all conversations on the same window (not required to, but it's my favorite way to fly), I can do everything with the keyboard, I don't have to move my hand to the mouse and then move it back to the keyboard then back to the mouse, etc. Just 2 handed typing with the keyboard. Because I can use a keyboard and type uninterrupted with both hands I am able to communicate very quickly as it's much easier and quicker to type then it is to move the mouse or talk. So, IRC and/or in person are the best options for me.
I don't like instant messengering, I don't care too much for email, and I hate the phone. Phones piss me off. There is no log or paper trail unless you write crap down or take notes. Yea, I acknowledge that I may be a bit on the odd side at times.