This thesis consists of three self-contained chapters covering topics in consumer theory. The first chapter presents an estimator for a Marshallian demand function which not only obeys all of the standard assumptions of consumer theory but will also converge to any true demand function which also obeys these standard assumptions. The second chapter explores Giffen behavior in the context of financial assets. The chapter finds that an agent with Maxmin preferences almost always displays Giffen behavior in some financial environments. Giffen behavior is also characterized for other classes of preferences. The last chapter, coauthored with one of my supervisors: John K.-H. Quah, develops a revealed preference test for weakly separable preferences in the spirit of Sydney Afriat. Unlike previous tests, ours does not impose concavity and applies to nonlinear budgets.