All you really need to play a roleplaying game is one copy of the rulebook, paper, pencils (Ticonderogas, please!) and the requisite dice. But it’s so much more fun to have additional stuff.
Knowing where your character is in proximity to the bad guys is important, so map tiles come in handy. Wizards of the Coast, publisher of Dungeons & Dragons, makes themed sets of map tiles out of thick laminated cardboard.
Paizo Publishing carries a line of Game Mastery tiles, easily affordable in thinner card stock. If you want to get really fancy, Dwarven Forge makes beautiful cast resin dungeon walls, floors, water features and accessory pieces of scenery, such as doors.
Lucite platforms and columns, called Combat Tier, are useful if you have creatures who can fly, or the need for characters to climb into the heights. They are marked with the typical one-inch-equals-five-feet grid.
Last but not least is scenery. I had great fun constructing this tavern for our Leviathan campaign, using some of the same materials for model railroad scenery.
What have I left out? What paraphernalia do you like to use in gaming? Comment below!