I suppose technically the first person was my ma. When I officially came out to her she told me that she remembered a moment when I was much younger and told her I was going to "grow up to be a boy named Tommy", at which point she told me that she liked Noah better. From my own memories, however...
First person was my third ex (at the time she wasn't an ex, I didn't even think we were in a relationship at that point), but admittedly that was largely because there were discussions of meeting in person while she was visiting family a couple hours away from where I live, so the issue was sort of forced. We don't really talk anymore, but that has nothing to do with my being transgendered: she was openly accepting and supportive of that. It's more, I suppose, a developed clash of personalities in a way.
Kind of toying with the idea of making my own "coming out" thread, to be honest...I wanted to include more but didn't want to post a novel here, haha!