Kovalev as a Panther probably makes the most sense as he played 14 games for them but to me it's actually the Senators that I forget about.
He did play almost two seasons with them, so it wasn't a short stint, but I was reminded recently and I had no recollection.
Svatos, McElhinney and David Hale were also alumni's of 2010-2011 Senators team that people probably forget or never even knew. Could count Derek Smith too but outside of Calgary I'm not sure anyone remembers he existed at all.