Ah man, this one should take some anime fans way back. I mean, this series aired when I was in elementary school and I wanted a giant fighting suit of my very own. Just maybe minus the Wing Zero Battle System, please?
#3 Gundam Wing
From 1995 to 1996, the original Gundam Wing series hit the US airwaves and man, what a classic it was to me. It followed the story of the protagonist Heero Yuy and the other Gundam pilots as they came down from the space colonies and began to battle the Earth forces in a super in depth plot line between the earth and space forces. The space colonies belonged to the Earth but they wanted freedom and the Gundams were sent down to make it happen (by force).
So what are Gundams? Well, they are giant robotic suits that are piloted by talented pilots that are able to use them in battle. See, in this futuristic anime the armies of the world and space use giant, mechanized suits for combat (no need for troops on the ground when you have mech suits that can do the walking for you). The Gundams are specially designed with better armor and unique weapons that give them the edge in combat. For example, Heavy Arms, the Red Gundam on the right of the above image, is loaded down with tons of guns, including huge Gatling gun, missiles and has combat swords and even a lightsaber type weapon that he can use in close combat. For a teen kid, this was such a bad ass series as they battled across the earth and into space.
It was an epic series and yes, there were a lot of other series that followed this one (Endless Waltz is trash, just wanted to put that out there), but Wing was the best series of them all.