I met a Tibetan Mastiff for the first time when I was twelve.  It was a black male.  Honestly, at first glance, I thought it was a bear.  Once I found out it was actually a dog, and that my life wasn't in any immediate danger, I was absolutely enamored.  From then on, I wanted a Tibetan Mastiff.

The males typically range from 120lbs to 160lbs, while the females are a bit smaller, usually ranging from 100lbs to 140lbs. They have large heads with very dramatic expressions.  The coat is long and typically forms a bushy mane around the head and neck, very reminiscent of a lion.  They come in a variety of colors (i.e. - black, black and tan, blue, blue and tan, red, gold or cream).

Their personalities are their strongest quality, though.  My little monster (pictured above at 8 weeks) is the sweetest dog I've ever met.  Now at 9 months old and weighing 100lbs (also pictured), he's wonderful to have around.  He's the best remedy for a rough day -- more than happy to give a soft and squishy hug.  He spends most of the day sleeping or munching on a bone.  He loves to play with other dogs or run up and down mountains.

I think for President Obama, the Tibetan Mastiff would make a great dog, because they're hypoallergenic and only shed for one three-week period during the spring.  That, and if they got a couple of these guys, they could probably fire half the secret service.

(Above I've attached a picture of an adult bred by Drakyi Tibetan Mastiffs to give a sense of what they look like full grown.  That one's not mine.)