Here is my code for drawing the region bounded by the sphere $x^2+y^2+z^2=1$ and the cylinder $x^2+y^2=x$.
one=Plot3D[{-Sqrt[-x^2 - y^2 + 1], Sqrt[-x^2 - y^2 + 1]}, {x, -1, 1}, {y, -1, 1},
ColorFunction -> {Red, Red},
RegionFunction -> Function[{x, y}, x^2 + y^2 < x]];
r[β_] := Cos[β];
two = ParametricPlot3D[{r[β] Cos[β], r[β] Sin[β], v Sqrt[1 - r[β]^2]},
{β, 0, 2 π}, {v, -1, 1}];
Show[one, two, BoxRatios -> {1, 1, 1}]
The result:

I'd love to see some other techniques if folks would like to contribute.
