Daniel Kahneman's dual-process theory — System 1 (fast, intuitive) and System 2 (slow, deliberate) — fundamentally changed how we understand decision-making. This article surveys the biases most dangerous in business contexts: anchoring, availability heuristic, loss aversion, sunk cost fallacy, and overconfidence. For each bias, it provides real-world business examples and practical debiasing techniques that teams can implement immediately, from pre-mortems to reference class forecasting.