I would prefer a Tiger or a Blue (they would require a smaller tank), but a Great White would definitely be one awesome 'pet.' Coming home after a shitty day at work to watch my little buddy feed on live seals would be so relaxing.
For a land pet I'd want a Gator. I'd name him Bubba and feed him my neighbor's yappy little rat terriers that seem to enjoy barking at 3AM every morning.