#3 Shield HeliCarrier
A flying aircraft carrier. Those four words alone would make any non comic-reader look at you like you're crazy. But S.H.I.E.L.D. has one and Nick Fury freakin' loves it. While the very concept of a "space craft" isn't that exciting, the concept of sea fearing vessel flying in the air is an entire matter altogether.

Powered by giant jets (often credit to Tony Stark), this behemoth can travel the globe. While hard stats are hard to come by, in the past we've seen that the Helicarrier is packed with a few hundred S.H.I.E.L.D. agents, jet fighters, missiles, escape pods, long and short range weapons (missiles), holding cells, and lots of fun 007-style equipment (jetpacks, etc).

Just to put this marvel in perspective (see what we did there?), and consider this: The standard Nimitz class Aircraft carrier in the US Navy fleet is estimated at 97,000 tons.

1 Ton = displace 210-256 gallons (800 to 1000 L) =  2,000 pounds (900 kg) = 60 cubic feet (1700 L) of space.

In the terms of tech, this is one bad momma.