Pests in your garden can quickly make a good day head south really quickly. The type of pest you have will generally vary by your location and climate. One major one for a lot of people are slugs and snails.
Thankfully, The Rusted Vegetable Garden has a great tip on how to use beer and yeast to eradicate those slimy little purveyors of doom and destruction.
[youtube=http://www.youtube.com/watch?v=lHmIj-s19M0]