If you do make a comment, they stare at you like you're from the moon. Your feelings have been building up for months -- maybe even years -- and it's time to do something about it. You can either pull your hair out over their obnoxious behaviors -- or, you can deal with them accordingly.

Define the Problem (aka "Co-worker")
In 'The Worst Case Scenario Survival Handbook: Work' (Chronicle Books), Joshua Piven and David Borgenicht describe four possible types of co-workers.

The Talker ... just won't shut up; engages in long-winded, one-sided conversations on relatively trivial subjects; and always has something to say about something (or someone).

The Kiss-Up ... craves approval mostly from the boss, but will also seek approval from you.

The TMI (Too Much Information) ... has no boundaries and no shame. He/she will share every piece of unpleasant and personal information with you, without sparing a detail.

The Gossip ... much like the TMI, will share any and every story -- as long as it's not theirs.

Deal With It
The following are some tips for how to deal with it if a co-worker is annoying you:

Tip No. 1: Take a break. When you are spending more than 40 hours per week indoors with the same people, something is bound to bother you. Everyone is going to have some sort of mannerism that bothers you, whether they crack their gum too loud or just hold their pen wrong. . Step outside for a breath of fresh air or run out to get a snack. It's human nature to get bothered by the little things, so just accept it and take a break.

Tip No. 2: Be mentally tough. Don't let another colleague's bad habits hurt your concentration and productivity at work. Drum suggests ignoring him or her as best you can and limiting your daily interactions with them.

If career advancement is important to you, then always try to act professionally in the workplace regardless of what an annoying co-worker might do.

Tip No. 3: Discuss the problem with your co-worker. (In a non-judgmental, non-confrontational way of course ...)
Don't be afraid to say something to your co-worker. Depending on what the behavior is that's bothering you, it never hurts to approach your co-worker for a friendly little chat, Co-workers sometimes don't notice they are doing something really annoying because it's just by habit. By saying, 'I don't know if you noticed but ... (insert issue here)' -- a reasonable co-worker will usually be receptive to your feelings.

Tip No. 4: Talk with your supervisor. If the friendly and polite one-on-one doesn't work (or turn out to be so friendly), another option is to bring up the issue with your supervisor.

From a managerial perspective, a difficult employee who is insensitive to other co-workers can poison a workplace environment and severely impact inner-office morale, Effective supervisors know how imperative it is to nip problems like this in the bud as soon as they arise.