Aegis. Even though it didn't last past his first SEED mode battle, the suit itself was still much better than all the other's he had has except for perhaps Infinite Justice. Four beamsabers, one built into each limb. A transformation mode meant for grabbing objects, as well as a chest cannon in its transformed state to completely destroy whatever he had grabbed, at point blank range even. If he activated the beamsabers while in transformed mode, he could sheer off all four limbs of the suit he was facing, before grabbing its chest and firing its cannon at point blank range (while it was never done specifically like that, I don't doubt Athrun's skill in pulling off such a manuver.) As well as the standard shield (which Tolle had the privledge of examining close up) and a beam rifle.

Infinite Justice sounds like it will have quite a lot of melee potential (unlike the original Justice, which I just considered no better than a Zaku with a booster pack so it could fly), which is why I think it might be even better, but I haven't seen it in action yet. ^^