Not all of us believe in such things. There was a recent discussion of this subject in this forum.
Hoods protect your lens from impact damage better than any filter. If you mean to protect from something else, such as to complete a lens' weather sealing, I use Heliopan multiple-coated UV filters, which are very expensive, but of good optical quality, which is necessary for night shooting if there are streetlights and such.
Canon 7D/5D/40D/1D2N; Nikon F6, FM3A, & Coolpix A; Canon 40mm Pancake, 135L, 50L, 35L, pre-II 50mm 1.8, 100mm 2.8L Macro, 10-22mm EF-S, 28-135 EF, 400mm 5.6L; Nikkor 50mm 1.2 AI-S, 50mm 1.4G, 50mm 1.8D, 16mm 2.8D Fisheye, 180mm 2.8D, 100-300mm 5.6 AI-S; Tokina 17mm & 100mm 2.8 Macro