Bride of the Rat God by Barbara Hambly
I reread this about every other year, and it gets better all the time. The characters are so layered, the atmosphere is magical and gritty (depending on the scene), the romance is low-tone and utterly sweet, and the action scenes are gripping.
Finders Keepers by Linnea Sinclair
Cinderella meets Farscape. One of the yummiest heroes of all time.
Nine Coaches Waiting by Mary Stewart
Another Cinderella storiy, this time set in the French Alps. One of the toughest decisions for the heroine I have read, and beautifully resolved.
Cotillion by Georgette Heyer
Freddy Standen, the best beta hero ever.