I've recently read/re-read the Infinity Gauntlet, Deadpool/Cable & Deadpool/Agent X, Onslaught Reborn (I might as well have shit on paper and read that instead), the majority of The Authority, Ultimate X-Men and Spider-Man.
If I don't get any wonderful suggestions I am going back to Uncanny X-Men 001 so please help.
Planetary - I cannot recommend this enough. If you don't like this then hurl yourself off a tall building as the world does not take kindly to the idiosyncratic.
Supreme Power - Justice League of America in the real world.
JLA; Brave New World - Obsidian Age- The best set of team books ever written
Wild Cats; Wild Worlds (Moore's Run)- If you like Authority you will love this.
Justice Society of America Johns and Robinsons run. Spectre eating entities that exist out of creation, the Flash stealing speed of Black Adam, A wizard who existed before time who moves the moon to put the earth in eternal darkness, need I say more ?
What he said plus All Star Superman, Captain Britain and the MI:13, Captain America, vol1 and 2 of Millar's Ultimates and Joss Whedon's run on Astonishing X-men