There's a subset of LF cameras called "press cameras" which were designed for hand-holding. There's a great website at Graflex.org that is a fairly comprehensive site for the Graflex press cameras. The Busch Pressman cameras were also popular. There were some others, but I can't remember much about them.
Originally Posted by Rinthe
That said, the vast majority of LF is tripod based. Why? The cameras are are often heavy, the shutter speeds are slow, and you can't use movements while hand-holding (it's nearly impossible to focus on a ground glass that's moving).