Staples in my kitchen - Tofu

Firm is good for stir-fries and deep-frying
Medium is easily blended and is good for sauces and desserts
Soft and silken is also easily blended and is good for desserts, dips, and sauces

Tofu is made from soy milk. I like the fact that alone it's practically tasteless, which makes it good a substitute or filler (try a silken version with your favorite recipe for Guacamole). Tofu is like a sponge, it will soak up whatever it's surrounded by and will take its flavor. Before preparing a stir-fry, I like to marinate cubed firm tofu, that has been deep-fried, in a sweet & sour and tamari sauce.