1. Ramban - V'chai B'hem - The way in which he treats and anticipates the reward of Mitzvos is the way he will be rewarded with a corresponding "life".
2. Ramban - Arayos - Provides reason for Arayos (not like Rambam); Promulgating humanity is the prime reason for "ishus" and arayos has intrinsic negative aspects for doing just that. Lastly, defines Chukim as having capability to be understood by select people.
3. Abarbanel - Arayos - Creating "unnatural" mating (like Kilayim) shares similar reason for the issur of arayos.