This is the kind of question that can get guys like me in trouble. I am limiting this to real dominas (not bodybuilders or escort/dominas I have seen). And for me these are ladies I have seen at least three times. They were and are ladies who had me experience things I never thought I would. And the locations were unique: dungeons, hotels, homes, in public and once on video. All were and are open and giving. And I trusted them. All were/are gorgeous in their own ways. The ones with an * are retired. They are not listed in rank order but chronologically.
Here goes:

*Mistress Belle de Jour – The legend. My first… Need I say more?
The late Mistress Ava Taurel – Met her through Belle and another legend. Intense and trusting.
*Mistress Ava/Lady Emmanulle – We did outdoor sessions at dawn on the weekends, before cell cameras
Empress Dominique – Spellbinding… and demanding
Mistress Rachel Fine – Imaginative and open, but in complete control
Goddess Severa – Physically intimidating, but a kind person. She is listed on the wb270.com because of her physical attributes and athletic training, but a true domina
*Goddess Vegas – Also met Vegas via wb270.com site but she was not a bodybuilder. A dancer, yoga teacher and athlete she dominated me physically and mentally up close and via long distance. I slipped into the deepest subspace with her that I ever experienced.