Not that any of this has ever happened to me...
  1. At a coffee shop, store, park or other public/semi public place.
    Not really awkward unless you really hate the co-worker. Like Tom in the mailroom. He's the worst.
  2. At a party of mutual friends you didn't know you had.
    Whoa! Wasn't expecting to see you here! Not a big deal though. How do you know the host?
  3. While on a date with your long term significant other.
    More annoying than awkward. You really wanted it to be a night out with your loved one. You rarely get alone time...
  4. In the bathroom.
    Inevitable but still slightly annoying. Plus Joe in accounting is a total talker too. I just want to do my business and leave. But he had to bring up Tom in the mailroom while we're both peeing at the urinals. Yeah yeah, we all hate Tom, he's a total gossip and is always giving us the wrong mail. But you're a close second since you never shut up and you always have coffee breath. Take a hint and accept my offer of an Altoid once in awhile will you Joe?
  5. On vacation, in your hometown (staycation).
    Slightly awkward because small talk is expected. "how's your time off?" That sort of thing. But at least it is not super surprising. After all you live in the same city.
  6. On vacation, away from your home city.
    Vaguely awkward. After all you wanted to get away from home. Are you obligated to say hello? Probably. But small talk is annoying because no one likes small talk. Inevitable "OMG! What a small world!" exchange must occur. Gah! I don't care why you are here in this city. No, I have no interest in hanging out with you and your cousin Fred while I'm here.
  7. On a sick day, when your not really sick but you didn't want to go into the office.
    Wait. Why are you here in the coffee shop too? Damn. Don't tell the boss. I'm really sick. *cough cough*. I just needed to run out and get tea. For my throat. *hides frozen pumpkin spice frappuccino behind my back*
  8. On a dating/hookup app
    Oh no! I never thought someone I KNOW would also be here! Now Joe knows I'm so desperate for a date that I'm on here. Wait. It's 2016. Everyone's on Tinder/Grindr. It's totally socially acceptable. It's fine. I'm just going to swipe...right. You know, just to see what he does. Fuck we didn't match. Can I take that back? Why can't I take back swipes?!?
  9. While on a date with a new love interest.
    Solidly awkward. You really want to control the amount of information and intimate details of your life that you reveal to the new love interest. Running into the coworker ruins that immediately. Really hope it's not Tom. He'll tell everyone.
  10. While on a blind date or a first date with someone you met online/via an app.
    Really awkward because everything about blind dates/1st time meets are awkward. Also I just broke up with my long term partner. So I'm very fragile.
  11. While on a date with another co-worker, that the office doesn't know about.
    Potentially really awkward. I mean, it's not against the rules in your office but you don't want to broadcast it. Crap! It's Tom who saw us! Great. Now the entire office will know I'm dating Joe. We're going to have to fill out that stupid HR form. It's not even that serious.
  12. At the gym locker room, while getting dressed/undressed.
    Um. Wasn't expecting to see Tom naked/have Tom see me naked. Let's just say hi and make sure our eyes don't drift too far down...Whoa. Tom has a better body than I thought he did! Better get out of here fast before something embarrassing happens....
  13. At a bar or club, dressed slightly slutty, slightly tipsy.
    Let's pretend we didn't see each other and this never happened. Wait. Tom, did you know you have a way better body than I thought you did? You shouldn't hide it with all that baggy clothes! Can I buy you a drink? Nah, Joe won't care. We're not exclusive. Wait. Where are you going? Shit. I hope he doesn't tell anyone about this. Oh damn, you know he will... Ooh they have shots! I'll take a couple of those...
  14. At an orgy/sex party/sex club/bathhouse.
    Unless he's really hot. Like Tom is. No actually this is just awkward regardless. Leave immediately. Doesn't matter if you got off or not. Just leave. Wait. Is he leaving? OK. I can stay now. Damn. I wish Tom had stayed...