How could you forget Viral? And of course, the powerhouse that is Libera Me From Hell. Though after listening to the GL OST again, I think Kill La Kill actually topped them.
I'd say that Gurren Lagann and Kill la Kill share the same spot on my favourite anime list, but Gurren Lagann just happens to be on the left. Both are excellent examples of ridiculous and entertaining over-the-top anime. Apples and oranges in the end I'd say.