I'll go by region.
Western europe - Claymore, easily. Big, beautiful, vicious swords. Designed not to hack people, but to hack horses. Often weren't even sharpened - you were supposed to break the horses legs, then kill its rider who would be pinned to the ground by the weight of his own armor. Usually between 54 and 60 inches in length, 9-15 lbs in weight, depending on steel used (mine is 1050 high carbon stage combat steel). Link:
http://cgi.ebay.com/ws/eBayISAPI.dll...category=20272 (this is not my auction, just one with a picture of a claymore)
Eastern Europe - Großmesser. Another big sword, though not quite as large as the claymore. Usually between 42 and 48 inches in length, 6-10 lbs. Single edged, slightly curved at the end. Used by german frontline soldiers to hack off the heads of pikes and to smash shields apart. Very basic design - straight wood handle, cast-iron guard, wide, single-edged blade. Link:
http://cgi.ebay.com/ws/eBayISAPI.dll...9&category=475
Asia - The chinese Dadao. This thing is just mean looking. Particularly Paul Chen's styled Dadao - it looks like a giant, fancy meat cleaver. Generally used two-handed because it's so top-blade-heavy. 28-36'', 3-6 lbs. These were used in China even up until the Sino revolution of the 1930's. Link:
http://cgi.ebay.com/ws/eBayISAPI.dll...4&category=475