I kind of have a love-hate relationship with the greedy Ferengi - in TNG I absolutely hated them, but DS9's Quark, Rom and Nog are simply a delight. Their Rules of Acquisition are ridiculously funny, let me give you a couple of examples:
80th rule of acquisition: If it works, sell it. If it works well, sell it for more. If it doesn't work, quadruple the price and sell it as an antique.
111th rule of acquisition: Treat people in your debt like family - exploit them.
208th rule of acquisition: Give someone a fish, you feed him for one day. Teach him how to fish, and you lose a steady customer.
281st rule of acquisition: Blood is thicker than water, but harder to sell.