Periodically the sink in the downstairs bathroom becomes clogged. This probably happens once a month on average.
Depending on who in our household you ask, the reason the sink clogs so frequently varies.
So that we're all on the same page here, the downstairs bathroom is my wife's bathroom. It has a a countertop with space for all her lady stuff like makeup and lotions and that assorted pile of bobby pins, loose earrings, hair ties and bracelets that have taken over the soap tray.
 The upstairs bathroom is unfinished, and has nothing but a two inch rim around a free standing sink upon which items may be placed. It's literally one step above a pale of water in the middle of the floor. Naturally that is the one I use.  
With the appropriate bathroom assignment situation's clarified, you can see where my wife's claim that the clogged sink is a result of the one or two times I have shaved my neck down there falls apart pretty quickly. 
Clearly the clogged sink is from a tangled clod of hair that made it's way from her head, to her hairbrush, into the sink where it slithered down the drain, and unionized or something and is now blockading the drain in protest preparing a list of demands for things like fancier conditioner.
Fresh from the rousing success of just having repaired a leaky kitchen sink, (a project that took three days instead of the twenty five minutes it should have) when my wife informed me the sink was leaking in her bathroom I decided I'd fix that and try to take care of that pesky recurring clog while I was at it.
Naturally after bumbling your way through one plumbing task, you should jump right into a second one, right?
So the job would be simple: Fix the leak, take the J-bend out and see if there is a pseudo-sentient hair amalgamation to extract, put it back together, stand back and stroke my glorious moustachio and beard in stoic approval of my own good work.   
Assuming that everything would go disastrously wrong I decided to chronicle the job. Below is the running diary of said task:
Day 1- Friday
4:00 PM
I decide to tackle the bathroom sink right after Emily leaves for work. Figuring I'd do it while she was out and have it leak free and draining like a champ by the time she came home. Thoroughly impressed with my rugged sink fixing man skills, there would proceed to be gallons of making out.
 4:05 PM
In my zeal for home repairing, at no point do I bother to run some water through the sink to locate the initial leak which had been reported to me. I have no idea what joint was actually leaking.
Figuring I'd have to take everything apart anyway in order to clean out wherever the clog is, I launch right into trying to take the pipes apart with a wrench. My assumption is that once the clog is dealt with, the leak will be sorted out when I put everything back together and tighten it.
I begin the process of attempting to disassemble the drain with the tools I have collected:
- Adjustable wrench x1
- Roll of paper towels x1
At no point does it occur to me that I have possibly under-prepared.
4:06 PM
I am unable to budge the joints holding the various pieces of pipe together with my single wrench. I probably need to get a second wrench to apply some force in opposite directions.
I own a second wrench.
Aforementioned wrench is in the basement.
I am not in the basement, I am in the bathroom.
That wrench can go f*@k itself. I'll make it work with the one.
Update 4:08 PM