Building great products requires understanding what users want and how they think. In this talk, we'll explore the essential engineering tools and cognitive biases that every engineer should know to build better products. We'll cover techniques like A/B testing, user feedback analysis, and product analytics, and show how they can be used to gain insights into user behavior and preferences. We'll use case studies of some popular cognitive biases to demonstrate these tools, and also see how we can leverage these biases to build products that our users actually love.