What is the best weapon on oblivion 4

There is no actual best weapon in the game but for swords would be the Umbra sword or the dusk/dawn fang because it gets better as you use it. As far as armor goes it would be Daedra, Imperial Dragon, Crusaders armor, or glass. It depends on what you want. Crusader has a lot of effects, Daedra, Imperial Dragon, and Glass all have a lot of protecting power.