Jason, you have a loose spoke... I can almost guarantee it. Flip the bike over, start at the valve and gently squeeze each spoke pair a little, they should all be taught... spin tire move to next pair and repeat. You will find one or more are loose and proably ready to fall out !
And your wheel is probably out of true.
People don't notice wheels being slightly out of true anymore with the advent of disc brakes (the v brakes required a true wheel, otherwise it'd rub)
anyway, if you want to tighten it with a spoke wrench, go for it... just do so carefully w/o stripping the nipple. and for the love of God, don't use pliers or your leatherman tool for this. :lol:
If I'm wrong, then you should bring the wheel into the LBS and let em have a look. Or if you don't want to mess with truing the wheel, bring it in anyway.