A very basic table with just four entries that I think is one of the most inspiring and useful things in all of Dungeons & Dragons.
Without this table all my adventures would be a bit less awesome. "A piece of jewellery worth 1200gp" is bland and stupid but "a gold necklace with an opal heart" is beautiful. This simple little table taught me the difference between a boring game and an engaging adventure, it taught me to make fun, exciting worlds filled with rich and interesting details. This little table made me the DM I am today. Thanks Jewelry Value Table (gp)!