Very tough question for me. I play clerics and holy warriors/adventures most of the time and throw myself into the roles.....
If I had to pick I'd say the triple goddess aspects are my favorite....virgin, mother, and crone.
In a recent Egyptian themed game I ran, I enjoyed running the cults for Bast, Hathor, and Sekhmet.
However my heart will always belong to a certain triple aspect goddess where I played a holy warrior in a home brew. Her name was Salustra and in this world there were two triple aspect goddesses. Salustra was the evil version. In 1st and 2nd edition I worshipped the white queen (virgin aspect), but in third I went for the Black Queen. The basic principle, beyond the normal for a druidic triple aspect goddess, for Salustra was the weak must perish for the strong to survive...a very Lawful Evolution (per dragon magazine 24 pg 32 Choir Practice at the First Church of Lawful Evil (Orthodox): The Ramifications of Alignment) mindset.
That isn't really how I believe, but I do believe in the tri-aspect goddesses.