Trail running partner...

I want a Savannah! I had a cat that was that big once. It also had the longest tail I have ever seen.

Jen, you can use Matey's picture as your computer's wallpaper, only temporarily mind you, as I know you will want to get your BRS wallpaper back up soon. Hee.
 
So far, Maine Coon cats and Savannah cats and Cheetahs (thanks Janson -lol) have been suggested. Any others?

We have a cat that is part maine coon. He is a turd. Hubby doesn't like him at all. Iwill even ship him to you!
 
I have a big fluffy gray former stray who will follow me about 1/4 mile down our road during the summer. Sometimes we 'run' into each other when i'm on the way back. He will stand in my way, circle around my legs, even claw at them, until I pick him up and carry him back to home, while sitting atop my shoulder (he's heavy!) like some kinda king.
Cats don't really run alongside, though. Even when they follow me around, they dodge in and out and aren't much company.
Like Rick said, they are too smart to follow a dumb human who is bothering to waste energy running in a non hunting related capacity. There's nothing in it for them.
 
I've also found that cats who spend much time outside will not be as tame as the ones who do. When my mostly outside cats are in a certain mood for play with prey, they don't just bat at cute little strings, they try to kill and eat me, just for sport(the other dumb human in the house is the one who feeds them mostly, anyhow, so what do they need me around for?), after they are done killing everything else in the neighborhood. Wouldn't want that with a savannah cat.