M is for Maps
Another letter where my choice of topics was a difficult one. But I had to go with a classic accessory for the game. While I know some people prefer not so use miniatures, even they tend to use at least a simple map to show players the layout of the rooms they enter.
Maps can take many forms at the gaming table. The Dungeon Master might consult a simple sheet of graph paper covered in his own sketch of a dungeon layout, or a more elaborate map published with a module, or other game accessory. For wilderness encounters, I actually prefer something like a flow chart of encounter locations rather than a detailed map of where each location is.
During the game, the DM can create maps for players in a variety of ways. They could sketch something on a gaming mat using wet or dry erase marker. Gaming Paper makes some great rolls of graph paper than can be laid on the table and sketched on. Either of these methods tend to use fairly simply mapping notations, though they can be done as elaborately as the DM would like. The gaming mat may be more flexible because it is a little easier to make changes to that type of map on the fly, but Gaming Paper has the benefit of being a bit more permanent in case you want to revisit a particular location again.
Game companies also produce maps specifically meant to be set on the table as a gaming grid for miniatures or tokens. These products tent to be full color with artwork to show a variety of dungeon dressings. Or you can get dungeon tiles, either printable online, or published on a variety of card stock or game board stock materials. These too are created with beautiful artwork, but are a bit more flexible than the printed maps because they can be rearranged, or stacked in order to provide a variety of room and corridor layouts.
There are even more elaborate methods of modeling encounter areas on the game table, but they move even further from the idea of being a Map, and will have to wait for another day.