http://www.thearma.org/spotlight/heymr.htm
scroll down a bit and you will find a picture of John Clements holding what is described as a "grossemesser or a grossesabel", the text to the pictures aswell as the pictures themselves tells you it is fit for both onehanded and twohanded use.
As it says, it could be a "grossesabel", I have seen some pictures of those someplace else (cannot remember where at the moment), the distinction between them and messers with a two handed grip is to me pretty vague ( due to my lack of knowledge).
in Albions new "maestro" line of swords a messer is displayed, in the description it says that:
"We can see from presentations in art that the Kreigsmesser was put to use in much the same advanced fighting techniques as was the longsword. These techniques were in no way crude or simple: the moves described require quick and expertly balanced weapons of offence and defence."
hope it helps somewhat.