Answer
$XeF_4$ is non-polar.
Work Step by Step
Xenon will single bond with each of the fluorine atoms, leaving two lone pairs on the Xenon. Generally, lone pairs prevent a molecule from being non-polar. However, in the case of $XeF_4$, there will be a square planar molecular geometry, causing the polarity of the Xe-F bonds to cancel each other out. The lone pairs of electrons will point in opposite directions, so the charges from the lone pairs will cancel out as well. Thus, the entire molecule will be non-polar.
