Does it have to be modern. My money is on the Mongols, or a phalanx of Pikemen. Don't forget the Roman Legion, or how about Sparta. If it's not man on man, how about the German Panzers, or any current modern nuclear armed submarine crew. Sci-Fi fictional - Fedaykin or Mobile Infantry (not the movie version, read a book people), or any Army commanded by Andrew Wiggin. How about those Air Force guys who fly the Spectre. Ninja's anybody. My list is endless. How about the Israeli Army of 1967 (6 Day War). Don't forget the Viet-Cong, brought the great o'US of A to a standstill. How about Che Guevara and his followers. If it's current modern military my money is on combat engineers. Put up a bridge while getting shot at. I digress.........best army in the world. Army ants. en.wikipedia.org/wiki/Army_ant
Practical experience no one beats the SAS period the end....and this is coming from a guy who's dad served as a sniper in the US Green Beret's. Seals and Beret's train the exact same, however the seals obviously are better in the water, while the Beret's excel in longer term deployments using counter insurgency techniques. That is a department no force in the world can stand against the Greenies in. The are called the silent professionals for a reason.
Spetznaz are not what they used to be sadly, that has more to do with the state of the Russian military and economy overall. Delta Force is right up there with the SAS as a strike force, but again the SAS has more time in the saddle so to speak.
In all honesty every branch of the military has it's own special forces. The only difference in their training is the terrain they are taught to fight on. Basically just take any special forces team from any branch of the military and they are probably some hardcore mother fuckers.
