Liquid Wrench is the old standby and PB Blast is the worthy newb. These two products work a little differently. L/W contains an acid, as I recall. These can take a few days, with heat applications in-between, to work in some cases. In extreme situations, fasteners can become permanently rusted together.
The best candidates for fatal rust-weld:
Handlebar nuts, some times one must choose between salvaging the handlebar or the nut and end up accomplishing neither
Axle nut, these can almost always be removed with heat & penetrating oil
Swigarm pivot bolt, pretty rare, but I have seen one so bad the even the bushings had to be replaced. Better to replace the swingarm.
Unless your bike is really rusty, you can expect to remove all of the rusted fasteners with little or no fanfare. If not, then check the frame carefully for rust perforations.