Gurren Lagann - Some plucky youth rebel against the systems that have forced humanity underground. Very over-the-top
Brave Bang Bravern - Extremely comedic and extremely gay, this is the story of humanity fighting against an alien threat with the help of a Super Robot who appeared out of nowhere seemingly from an entirely different genre of anime
Eureka Seven - A boy joins a band of rebels to fight the world government in their hover-surfboard-riding mechs
Vision of Escaflowne - Of the two prominent 90s mech shoujo isekai, this one is by far my favorite. Who knew putting a cape on a mech would make it look so gallant?
Some of my favorites:
Thank you! I won’t run out of anime so soon now :D