Keanu and Morgan Freeman - Chain Reaction
Morgan Freeman and Christian Slater - Hard Rain
Christian Slater - Star Trek: The undiscovered Country
Bruce Willis and Harlan Ellison--"Shatterday."
Harlan Ellison and Shatner--"City on the Edge of Forever"
(Oh, just to show off, you can do Keanu in two steps. He was in SPEED with Sandra Bullock, who did MISS CONGENIALITY with Shatner.)