Other than the army, I'd have to say that was during my tenure as map maker and surveyor. Firstly, I had a boss who hired me fresh out of college with the knowledge that I had zero experience with surveying or even using AutoCAD. AutoCAD took me no time to figure out, but he was entirely too busy to teach me a damn thing
We had another guy, from Quebec, also fresh out of college. He was about 7 years older than me. Let's call him Pierre. Pierre had been on medical leave for 4 months when I started. He had been working there for 4 months prior to taking his leave of absence. Pierre had migraines and they affected his equilibrium. He also weighed about 450 pounds, my boss told me, after he came back, that he must have gained 100 pounds in the 4 months he was gone. The doctors never could figure out what was wrong with him.
Pierre came back to work slowly, for the first month or two, it was only for 3 hours a day. It incrementally became an 8 hour day for Pierre. Right from the get-go, Pierre thought he was my boss. He would ask me to perform pretty mundane tasks and for a little while, I just rolled with it. Figured I was the new(est) guy and I'd just earn my keep. It quickly became clear that Pierre had just as much of a clue as I did (next to none). Once that was established, I never let him interrupt me from what I was doing. I was working way more hours in a week than he was and I was not going to let this dude feel like he was my boss. I was on the road most days of the week, working 10 hour days, working 60-80 hour weeks, and going out into the field in the hot southern sun while this chuckle fuck sat in the AC for 3 hours a day eating candy bars.
Things came to a head the friday before Memorial Day weekend. Pierre wanted to show me something on my computer, we were collaborating on a map, and I told him to click "save" but to not, I repeat not click "save as". What did this motherfucker do? He clicked save as. So I proceed to fucking flip out. I was 15 min away from finishing my days task and going home early, he just saved over 4 hours of work. He tried to blame it on the language barrier, he learned pretty fast that I can cuss someone out in French, even Quebecois. After that, we were mortal enemies.
The next week I noticed Pierre started showing up earlier than I did. Whatever. But I also noticed, I wasn't getting much work. Later found out Pierre was stealing work from me in an effort to make me look bad. See, it was difficult to get 2 min of my boss' time. He was constantly out of the office or on the phone with surveyors or customers. Usually he'd give the days work to whoever showed up first and have them divvy it up between CAD guys. So when Pierre would show up first, I'd ask him what he had for us to do and he'd say it was all his work. Took about 3 days for me to figure it out, another week for me to even be able to talk to my boss about it.
Anyhow, the last time I saw Pierre he had walked into the building looking white as a ghost and sweating profusely. He was complaining of a stomach ache. He stood up and almost fell over so we call an ambulance and the paramedics naturally assumed appendicitis based on his symptoms. So they gave him a MRI and found out he was just really constipated. I worked there for 8 more weeks before finding a better job and he still hadn't gotten the okay from a doctor to come back. Never found out what happened, but my boss was saying the company couldn't hang on to him much longer, that he was a liability for them.