(Just scanning through posts, see what pops up)
1. For lower-powered Quicksilver, then Mammoth wins (QS doesn't have any real way of hurting him, while if M can get even one lucky, solid hit, QS goes down). For later/much faster versions, then QS, though it might take some time, as M is pretty tough, and will take a lot of high-speed beating.
2. A tough call. Hulk isn't simply really strong, is also very durable. But Vision might be able to take him down with a phased-attack. Like posted above, depends on which version.
3. In a "short" fight, Cap, definitly. But if Fire Star can get airborn and dodge at least one shield toss, her raising the ambient temperature in the room/area by several hundred degrees is going to put a crimp in even Cap's style... and by crimp, I mean sudden heatstroke.