One of the biggest influences on me has been Neurolinguistic Programming (NLP), a modality based on the work of hypnotherapist Milton Erickson, family therapist Virginia Satir and Gestalt therapist Fritz Perls.
In fact, Tony Robbins started with NLP and was one of the first coaches to use it as a tool for business success as opposed to using it as just a tool for therapy.
What I particularly like are the presuppositions, which are a bit like the ten commandments. Christianity won't really work for you unless you follow the ten commandments. So too, NLP won't work for you unless you accept the NLP presuppositions.
Some of my favorites are "Beliefs don't have to be true, just useful', "All memories are myths", "The map is not the territory" and "The meaning of the communication is how it is received".