Players that were major chokers but improved mentally.
I'm not just talking about in slams (like Clijsters) but all the time. The ATP have Berdych & Soderling - two players who got to the top 20 on mostly talent alone and were weak mentally but improved that area and moved up to top 10 level.
I think Petkovic had quite a choking thing going on for a while. But she was putting that to rest quite well before she got injured.