Janner18, cyclist Molly Cameron is interesting. She tried to race with women, but at the time (2008) she wasn't allowed to as the rules stated then that only men with GRS could complete as women.
So she went back to competing (quite successfully) in the men's events. Until 2015 when she was told she could no longer compete as a man because her birth cert and passport now said "female"
. (using "she" as otherwise the whole thing gets confusing)
It's also worth mentioning wrestler Mack Begg who was born female and is still competing in women's events despite taking testosterone and other drugs as part of his transition. As far as I can see if he was still claiming to be female he'd be banned for cheating, so the rules are, at best, confusing.
It will be very interesting to see how he manages when/if they do move him to men's categories - though I suspect in a sport where weight categories sort things out a little bit, he'll do better than he would in a sport where all men are put in together and he might be facing someone twice his height and weight.