Erasable Pens
Now you see it, now you don't!
With most modern erasable pens, friction is used to remove the ink neatly and cleanly. The key? Thermo-sensitive ink, as pioneered by the Pilot Frixion. Applying friction to anything written in this specially-formulated ink - usually by using the pen's incorporated eraser - results in a rise in the temperature of the ink, which consequently becomes transparent. Lines are removed quickly and cleanly, and what's more, if you stick your paper in the freezer, the drop in temperature means the lines will magically reappear!
And yes, this does mean you shouldn't rely on erased writing staying erased - these aren't to be used when you want your words gone and staying gone.
But the result is that not only can you erase more easily, but the original writing experience is much nicer too, just like any other gel pen or rollerball. Erasing is clean, and the 'eraser' part doesn't wear away after a bit of use.