OK, I'll throw one more on the pile, my first all-grain batch.
The screw-ups start on brew day, as we're transferring the cooled wort to the fermentation bucket. I'm so excited/nervous about using the fancy ball valve on my brand new brew kettle that I completely forget I need a hydrometer sample for an OG reading until I've already drained half the wort.
My brewing partner and girlfriend is here helping, so, no worries, right? I ask her to grab a little glass to hold the sample while I keep an eye on things at the kettle, she brings it back, holds it over the fermentation bucket near the stream of wort... then, we completely fail to communicate who is supposed to be holding the glass, and, *SPLASH!* into the fermentation bucket it goes.
At this point, I figure, what's done is done -- any bugs on the glass will have floated off into the wort in the first second or two, and I can only introduce even more contamination by reaching in there after it. So, we leave the glass, get another one under the wort stream in time to pull the hydrometer sample, pitch our yeast, and call it a day.
Fast forward a couple of days, fermentation is proceeding well -- a little too well, in fact, there's krausen goop starting to get into the airlock. I'm sure you all know where this is heading... I pull the airlock and rubber bung, clean 'em, sanitize 'em, and make that popular mistake of putting the bung into the bucket lid and then trying to insert the airlock. *PLOP!* in goes my only bucket-lid-airlock-hole-sized bung, to keep that sample glass company.
Did I mention that it's the afternoon of Christmas eve?
So, yeah, here I am, holding my now-useless airlock in my hand, LHBS is already closed, won't be open on Christmas Day, 36 hours before I can possibly get a replacement bung. I throw a little glass bowl over the airlock hole in the hopes of at least making it harder for the nasties to drift into my beer, then it's off to the folks' place for Christmas Eve dinner.
After spending the next 36 hours periodically cleaning copious amounts of krausen goop off the top of my fermentor, hooray, the LHBS is open, I can pick up another bung, rig up a blow-off tube, and RDWHAHB. If there's a silver lining to cleaning up sticky, drippy krausen goo, it's that doing it in a room that smells half like porter and half like rising bread ain't all bad.
Well, it's a few weeks later, and I just racked it to secondary last night. I don't think this beer will every be "great" -- some unrelated growing pains in my all-grain process and some overzealous temperature control have kept this batch from fulfilling its full potential. But none of my hydrometer samples had any trace of funk or sourness, and there wasn't any sign of pellicle formation, in spite of my multiple poorly-timed attempts at infecting the batch, so, I'm confident this beer has a bright future ahead of it.