This is actually a hard one to call. As much as the Matrix fanboys will hate me, Neo goes down first, as he is the only one that can still genuinely be hurt by conventional weapons like swords and guns (if only temporarily in some cases). He dies first, based on durability/damage soak/regen.
Surfer and Manhattan... depends whose molecular manipulation abilities and overall power output trumps whose. Really hard to say here. Based on screen feats of Surfer killing Galactus, I am leaning towards him.
Mask is actually the wild card here. I haven't seen the movies in a while, but the wearer literally has toonforce IIRC. Which means they are invulnerable while wearing the mask, and can do whatever their imagination can come up with. So, in theory, the wielder (if creative enough) can literally pull a "How to kill Surfer/Manhattan" manual out of their ass, and use it to find out how to stop those 2. It all depends on the wearer.