Thank you for the thoughtful question.

Time travel is theoretically possible, but there are many people far smarter than I am who would debate that. According to Einstein's Theory of Relativity, space and time warp if one were to travel at speeds in excess of that of light. The astronaut in question would experience time slower than those of us here on Earth. Whether or not humans can travel between two points, either forward or backward, in the space/time continuum is the cause of both serious study and beer-fueled conversations between sci-fi obsessed physicists.

There are pop scientists like Stephen Hawking and Carl Sagan who have suggested that if time travel were possible, we would have been visited by time travelers already. Sagan, specifically, suggested that those time travelers might be in disguise. I don't know why time tourists would visit 2010. Maybe to watch a human use an iPad for the first time? Or to watch us squirt lead at one another over the dinosaur go-juice we need to power our non-flying cars? I have this terrible feeling that a 1,000 years in the future, our entire civilization will be remembered for one thing: Tila Tequila. She will be held up as our Cleopatra, the figurehead who best represents all we stood for as a people. So maybe time travelers would want to see that loathsome porno Oompa-Loompah in the flesh.

That said, if they ever sell personal Flux Capacitors, I am the first in line. I'll be the cyborg with the giant pincer-like crab claws.

To answer your question as to which kind of time traveler I'd be... both "the kill Hitler" and The Butterfly Effect kind are sort of the same, no? First of all, many nerds would argue that going back in time would just serve to create a parallel reality where your actions have effected the outcome of history, from the point of your arrival. So if I went back and killed Hitler, there would still be a reality where that madman survives. And who's to say there wouldn't be a Nazi in the wings even worse than Hitler? There's ample evidence that factions within the Nazi party grew tired of Hitler's increasing meglomania as World War II raged on. If I went back and killed Hitler, who's to say one of those nutjobs wouldn't have turned out to be more Hitler than Hitler. Hitler-er!

The Butterfly Effect is both an excellent movie starring Mr. Demi Moore, and the idea that a butterfly fluttering it's wings can create a tsunami wave a world away. Our actions reverberate. They matter. Killing Hitler would set off a series of events that could destroy the world, instead of merely wrecking it for generations.

That said, if I could time travel, I'd be tempted to go back in time and try to repair some of the epic mistakes I've made in relationships. I've made people I love cry. I've done things that I deeply regret. I've needlessly broken hearts and taken hammers to my own. I have been a very selfish, thoughtless, and careless man. Experience is never making the same mistake six or seven times. Wisdom is scar tissue that warns you not to juggle knives drunk again. So I imagine being able to travel back in time and telling myself that her love is worth more than that other's body. I'd tell myself not to ignore the toxic whispers and gossip of the mob. Listen to her. Don't walk out. You're being a mega-dickface. I'd save myself a pitcher of tears, that's for sure. There are parts of my life rendered lifeless with the radiation from my bad decisions.

But according to the theory I mentioned earlier, there would still be a reality where I learned my lessons the hard way. Which would be this reality. So, in one way, there's really no way to back to the past and make it right. You can only look to the future, and hope that tomorrow's yesterday is brighter than today's sorrow over what can't be undone.