People who know about the different schools of Buddhism are often curious which one I belong to, so they'd ask me, "What type of Buddhist are you?" And I would say, "A lousy one, of course."
In truth, I think I have benefited tremendously from all 3 branches of Buddhism.
I benefited tremendously from the concreteness and clarity of Theravada Buddhism. Theravada scriptures are the closest thing we have to the original teachings of the Buddha, the greatest hero in my life. Theravada teachings are systematic, logical, highly accessible, historically authentic, and contains minimal amount of the magic and mystery I found distasteful. The Vipassana practice (a somewhat relaxed version of which became known as "Mindfulness meditation" in the West), which comes out of the Theravada tradition, is the single most important thing I have learned in my entire life. Theravada teachings form both the theoretical and practical foundations of my Buddhist practice, from which I became able to understand and appreciate the other schools of Buddhism. Theravada is my root, my foundation. This is the body of my practice. The body of my practice is Virtue, Concentration and Wisdom (Sila, Samadhi and Panna).
I benefited tremendously from the inspiring power of Vajrayana (Tibetan) Buddhism. Vajrayana Buddhism is the result of at least two major rounds of evolution from the original teachings of the Buddha (either evolution or degeneration, I'm happy to argue either or both) and includes many important refinements and additions to more traditional forms of Buddhism. In many ways, Vajrayana is Buddhism on steroids. It has awed and inspired me. It has given me my Compassion practice. It inspired me to take my Bodhisattva Vows. Vajrayana is my thunder, my power. This is the heart of my practice. The heart of my practice is Emptiness and Compassion (Sunyata and Karuna).
I benefited tremendously from the simple directness of Zen Buddhism, which is, in my opinion, the greatest of all the Mahayana schools. True wisdom is simple and full of lightness and humor. Zen embodies it. Just be. Enlightenment is the perfection of just being. Zen is my no-self-ness (无我). This is the soul of my practice. The soul of my practice is. Just is.
Hence, I belong to all 3 major schools of Buddhism. At the same time, I belong to none of them. My true Dharma is the Hahayana. Ha ha.