Management may disagree, but these are valid.

• Feeling panicky because you learned that a bounty hunter is in town looking for you, and he knows where you work.
• Feeling panicky for no good reason and you can’t control it.
• Feeling panicky because you know you have to go to the bad place and clock in.
• Feeling depressed and hopeless and unable to get out of bed
• Contemplating suicide, and know that removing your ability to think things through in a constructive way because you are around people all day long might take you one step closer to the last step.
• Too many thoughts, which will inevitably result in staring into the middle space until someone notices and asks what you are doing, and it will be impossible to explain what is going on in your head, what you are actually doing, and this is an actual predictable thing that will happen which should be avoided.
• Allergies and any other unpleasantness of the nose, diagnosed or otherwise.
• Medical conditions that cannot be seen, like STIs, or cancer, or any mental health condition, all of which can be valid reasons to miss work.
• Quiz: Are mental health conditions valid reasons to miss work? Answer: Yes, the federal government even says so. 
• Overwhelmed by work because someone treated you bad the day before. 
• Overwhelmed by life, just need to do your own shit for a day without any interruption. Many people think this is an irresponsible reason to call out, but that’s just because they were feeling fine that day. We all need this day sometimes. Be reasonable.
• Resignation letter not finalized.
• Steve.
• Car accident, plumbing problem, electricity about to be shut off, any one of thousands of unfortunate car problem, childcare issue, family emergency, freezer defrosted, water/electricity off, child trapped in well.
• Found rich vein of gold directly under apartment while violating tenant rules and digging a hole in your living room. Need to mine as much as possible without getting caught before giving notice and moving to Aruba.
• They treat you like you are an unimportant cog every day, so fuck them if they don’t want to treat you with respect then they can live without you for a day. 
• On last chapter/episode of book/show.
• Reckless abandon.
• Unrequited sexual opportunity.
• Attacked/infested by wildlife.
• Don’t want to get caught not working.
• You are imagining hurting people or things at work.