Currently, no one. My wife just isn't into it (though she's into plenty else...).
In the past, though, I've had GFs who got into watching me, as part of sex.
Also, I had one GF who would masturbate herself every so often with me around, but w/o much expectation that I join in (e.g., I'm late for work, she's just getting up, no chance of me 'lingering' to play...). After awhile, I just started doing the same around her. It got to be a little game sometimes. Once we both got ourselves off driving together to have dinner at her parents (unspoken rule was, don't touch the other person... weird, I know).
The only other people I've been able to jack off openly around openly were my brothers when we were younger. We're three in a row, none of us more than 18 mos apart from the next oldest/youngest, so we pretty much got used to spanking ourselves (but never each other) no matter whether another or both of the other brothers was around. For awhile we even had a common "spank drawer" in a desk in our study/play room. On the top were some boring school textbooks, but underneath we kept a common stash of porn, lube, hot pics of girls we knew, etc. One of my brothers jacked off so much, my other brother and I nicknamed him "Spunky." The nickname stuck (pun intended) all the way through high school. My Mom even used it every now and then (cluelessly, of course), which was pretty funny.