Worst thing you've seen another dev do? Here is another.

Early into our eCommerce venture, we experienced the normal growing pains.

Part of the learning process was realizing in web development, you should only access data resources on an as-needed basis.

One business object on it's creation would populate db lookups, initialize business rule engines (calling the db), etc.

Initially, this design was fine, no one noticed anything until business started to grow and started to cause problems in other systems (classic scaling problems)

VP wanted a review of the code and recommendations before throwing hardware at the problem (which they already started to do).

Over a month, I started making some aggressive changes by streamlining SQL, moving initialization, and refactoring like a mad man.

Over all page loads were not really affected, but the back-end resources were almost back to pre-eCommerce levels.

The main web developer at the time was not amused and fought my changes as much as she could.

Couple months later the CEO was speaking to everyone about his experience at a trade show when another CEO was complementing him on the changes to our web site.
The site was must faster, pages loaded without any glitches, checkout actually worked the first time, etc.
CEO wanted to thank everyone involved etc..and so on.

About a week later the VP handed out 'Thank You' certificates for the entire web team (only 4 at the time, I was on another team). I was noticeably excluded (not that I cared about a stupid piece of paper, but they also got a pizza lunch...I was much more pissed about that). My boss went to find out what was going on.

MyBoss: "Well, turned out 'Sally' did make all the web site performance improvements."
Me: "Where have you been the past 3 months? 'Sally' is the one who fought all my improvements. All my improvements are still in the production code."
MyBoss: "I'm just the messenger. What would you like me to do? I can buy you a pizza if you want. The team already reviewed the code and they are the ones who gave her the credit."
Me: "That's crap. My comments are all over that code base. I put my initials, date, what I did, why, and what was improved. I put the actual performance improvement numbers in the code!"
MyBoss: "Yea? Weird. That is what 'Tom' said why 'Sally' was put in for a promotion. For her due diligence for documenting the improvements."
Me:"What!? No. Look...lets look at the code"

Open up the file...there it was...*her* initials...the date, what changed, performance improvement numbers, etc.

WTF!

I opened version control and saw that she made one change, the day *after* the CEO thanked everyone and replaced my initials with hers.

She knew the other devs would only look at the current code to see who made the improvements (not bother to look at the code-differences)

MyBoss: "Wow...that's dirty. Best to move on and forget about it. Let them have their little party. Let us grown ups keeping doing the important things."