There were plenty of two handers during the 15th and 16th centuries, though longswords were more popular. I'd hesitate to limit anything to just a "knightly" sword. An M-16 is an M-16- it dosent change names if you are a soldier or a civilian. Each sword has things it does well and things it does less well, or not at all.
You might want to take a look at Albions website and look for swords like The Chieftain, The Mercenary, The Agincourt, The Talhoffer and others for some ideas. These are more longswords than true two handers though. Albion has one called The Dane that would certainly be a true two hander. Scottish two handers are generally in this category though many are more the shorter, longsword variety.
Another option is the Tuck/Estoc which is a very thin and very stiff , edgeless blade that is used to thrust into armor gaps more effectivley.
http://www.myarmoury.com/albums/display ... m=41&pos=6
"Why is there a picture of a man with a sword in his head on your desk?" -friends inquiry