The Ghosts of SNL Presidents Past
The most recent Funny or Die original accomplishes something other than being funny or dying: It unites four(!) generations of legendary SNL cast members in the same room together. Quite a feat. Oh, and it's really funny.
Funny or Die's Presidential Reunion from Will Ferrell
Also, Reagan's balls are one of the better sight gags I've seen in a while. They look like baseballs in tube socks!