Abraham Lincoln - I think he would be good company, and it would be interesting to see his reaction to all that has unfolded since he died, from Reconstruction through the westward movement and the closing of the frontier, through the 20th century with all its tumult, to Obama.
Queen Elizabeth II - An odd choice, but this is a woman who, merely by virtue of birth, has known every significant world leader from the 30's through today - Churchill, Eisenhower, Truman, Roosevelt, Kennedy, Nixon, Thatcher, Reagan, the Bushes, Blair; who knows a huge chunk of the worlds' secrets, from nuclear strategies through the minutiae of world diplomacy; and keeps those secrets; who occupies a completely anachronistic but still historically interesting position. Imagine the stories she could tell, if we could get a couple of gin and tonics in her and loosen up her legendary discretion.
My dog - It would be interesting to see what he thinks of me, as well as my family. I would love to know what things he likes to do, swimming, running, walks.