No matter whether you have a mustache, beard, or neither, you'll want to pick up a pair of grooming scissors. You'll be amazed how much you'll use them.
We at faveable love this pair of grooming shears from Tweezerman. They're made of lightweight stainless steel, so they're easy to use and pretty durable. Even if you don't have a lot of beard growth, they still come in handy for bushy brows and the occasional stray hair.