Actually, I forgot to mention the phone in my comment, but I think it's probably the worst for me as well, except possibly reading aloud (although, interestingly enough, I think reading aloud over the phone wouldn't be quite as bad for some reason, although I haven't actually tried it). I haven't used the phone in a very long time, which is probably why I forgot to mention it, and don't plan to any time in the foreseeable future. I think one of the main points about the phone is that it's very hard to portray that you're stuttering and not just stalling, being cut off by some network/static issue, or just done talking. The risk of being interrupted, cut off, misunderstood, etc is much higher over the phone, and I think that contributes a lot to the stress.