If you've ever laid out the cash for good quality optics – be it a camera lens, binoculars or upgrades to the Hubble space telescope – you know all about sticker shock. Once you've ponied up, doesn't it make sense to take care of your new baby? Don't procrastinate, get a lens pen.
The LensPen UltraPro is inexpensive and includes the basics: a protractile (shut up autocorrect, is too a word) goat-hair brush – yeah baby, goats! – to shoo away the vicious scratching particles clinging to your lens, and a carbon something-or-other felt-like material to gently polish and absorb oils or whatever nastiness you've managed to contaminate your lens with.
Lens caps cover both ends, inexplicably screwing on for the brush end and just a friction fit for the cleaner end. There's a handy-dandy pocket clip and you're good to go. Seriously, just buy a couple and keep them in your camera bag, range bag, bino case or wherever you'll be sure to have them handy when you inevitably need one.