David Wills was a lawyer and the man mostly responsible for the creation of the national cemetery at Gettysburg after the battle. It was he who invited President Lincoln to the dedication ceremony, as an afterthought--the main speaker was to be the great orator at the time, Edward Everett. Lincoln stayed at Wills' house the night before the dedication ceremony, and legend has it he finished writing the Gettysburg Address there at Wills' house, though no one knows for certain.
Wills didn't fight in the battle, or the war at all (that may have been John Burns you're thinking about, as Tom said). He grew up near Gettysburg, went to Pennsylvania College (which is now Gettysburg College) for law, and then worked as a law student in Thaddeus Stevens' law office. He opened his own law office in Gettysburg in 1853.
The David Wills House is the newest "jewel" in the Park Service crown at Gettysburg. It was opened on the Diamond/Square about a year ago. There are lots of artifacts related to Wills and his family, and also Lincoln, and you can see the bedroom (rennovated) where Lincoln slept the night of November 18, 1863.
I was lucky enough about a year ago to see other artifacts from David Wills at the Adams County Historical Society in Schumaker Hall on the Lutheran Theological Seminary campus. I particularly liked the scarf and hat that Wills wore at the dedication, and also the scarf/muffler that his wife wore, as well.