Well, the obvious answer is a Naval Rail gun. I'm a big proponent of rail guns...
Err... Naval Rail guns... stats::
will shoot a 4"x4"x4" block of metal... 0 to 10km/sec in 1ms, (In American measurements, that's 0 to 22369.36 miles per hour, or 6.213712 miles/sec in 1ms) the metal liquifies before it is out of the rail, it will go through 20 tanks no problem, has an effective range of 200 miles shot FLAT horizontally, and the ammo is cheap, scrap metal is just fine. It will go through roughly 5 miles of anything, buildings and the like, and just basically is the electromagnetic afgan nightmare from hell..
http://members.home.net/crandon/railguntech.html
Come on, you KNOW this is the way weapons are heading...
Or just do the most american thing there is, a nice 50Caliber BMG shot to Bin Laden's head... I mean God gave us John Moss Browning for that reason right??
Albert