Hard to say, as tanks aren't what you would call beautiful vehicles.
But, ok, I'll play your little game.
![Tongue [:P]](/FSM/CS/emoticons/icon_smile_tongue.gif)
Purely in terms of looks, I'd have to say either the Abrams or the Swedish 103-C. For WWII, the Jagdpanther is an elegant vehicle.
You didn't ask, but tanks represent military forces, and so I would consider them to be a little too politically controversial for the office. (This is assuming "the office" means an office at a company, not your private office at your house. If I'm wrong, don't bother reading the rest of this!)
I work at a Japanese bank, and so anything from WWII is completely out -- Allied stuff, of course, but also Axis stuff, as the Japanese are deeply ashamed of, and have repudiated, their fascist past. Not because I am afraid of getting in trouble, mind you, but out of respect for the feelings of my co-workers.
I have a good friend who is Palestinian, and she has some pretty bad memories of Israeli military vehicles. I won't get into details, other than to say that she doesn't live in her homeland any more. She was driven out, as were so many others, by the impossiblity of living anything approaching a normal life in her homeland. I wonder how someone like her would feel if they walked into your office and saw an Israeli tank there.
Hey, I know you are just interested in military history and hardware. The other guys here know the same thing. But the folks in the office might not know that. Not meaning to bud into your private decisions or to ruin your fun project, but just offering this as food for thought. Tanks are built to kill people, and they often do just that. You never know who may have stared down the muzzle of the real thing you've got a model of on your desk, when she was a nine-year-old girl.