Despite everything your college friends told you, you should not ask for "Das Boot" in a German beer hall. They're likely to give you a submarine. The German word for boot is stiefel and the epic two-liter beer drinking glass is more formally known as a Biersteifel.
The origins of the stiefel are cloaked in various legends. One take is that a German general promised his troops he'd drink out of his boots if they prevailed in a coming battle and both the troops and the general held up their end of the bargain. A second theory had troops in battle drinking out of their boots with no other vessel at hand. The most persuasive story we encountered came courtesy of the Gordon Biersch Brewing Company: As they would have it, sixteenth century German fraternities would settle disputes with duels. Afterwards a member of the fraternity would take off his leather boot and drink from it while his friends cheered him on and sang "The boot must die."
Whatever the origins, at some point hygiene took a bit of a step forward and boots were created out of glass. They're still too big for most people to drink alone though and all kinds of drinking rituals and games attend the use of a stiefel in a group setting. House rules prevail at all times, but the most common rules dictate that the steifel may be held with just one hand and may not touch the table once lifted off of it for the first time. The last person to pass the stiefel before it gets finished is usually responsible for purchasing the next one.
One tip: Drinking out of a stiefel with the toe pointed up will result in an air pocket bubbling up into the toe and splash of beer in the face. Make sure the toe is pointed down or sideways and physics will remain your friend.
What it's best for: Drinking relatively low-alcohol German styles like Munich Helles or Dunkel in a group setting.