1. Elder Scrolls Series. While sometimes they are individuals you purchase commodities and crafting items, most of the time you use them as places to dump surplus loot in exchange for gold, despite the fact that it is inconceivable that they can manage to sell off their inventory.
EX. I think all good Skyrim players try to balance the following process: picking up loot from containers (including the dozens of corpses you encounter during your average adventure) so that you can get the most gold per pound of weight carried, even going so far to use magical items/perks to increase carrying weight, then taking that loot to several merchants in order to get them to buy as much of your useless gear as possible so you basically bankrupt them (I often buy crafting items from them so that I can sell them useless stuff), and then repeat the process ad nauseum.
Pro Tip #3,105: Make sure to pick up arrows that are worth any amount of gold. They have no weight, so you can carry a practically limitless amount, are always useful (archery has and will continue to be broken in the Elder Scrolls series), and are often worth a good chunk of change.