I think single issue voters are silly.
Issues for me are weighted, and the gun issue has a LOT of weight, as compared to other issues (abortion, gay marriage, etc) which have very little weight.
So, for instance, if a candidate came around that I felt was right on the gun issue, taxes, immigration, shrinking of government/expansion of freedoms and energy (an example of highly weighted topics) , but was wrong on abortion, gay marriage, gays in the military, drug policy (an example of lowly weighted topics for me), then I could probably vote for that candidate.