I made all my worst mistakes in the same brew!
1. Not testing the tap on my fermenter before racking in the wort.
To make matters worse, I left the room during the transfer, so returned to find the best part of 5 gallons sitting in a leaky bucket. I panicked, and rather than pour it back into the boiler, I stuck my arm in (yes, ewww) and tightened the nut. Sticky floor afterwards, but most of the brew remained in the bucket. I didn't chuck the beer (was my first AG so I was determined to keep going) but...
2. Naturally, the beer came out sour. Turns out hairy arms are full of tasty wild yeast. 'No worries' thinks I, I might save this by making a fruit beer - I've never made one. This was another error in itself, but it gets worse...
3. So I trot off to the supermarket and buy me some bananas. Why bananas? Because cherries are damn expensive and I couldn't be arsed to clean and chop apples. I chuck the bananas in, and go to work the next day. The lid is on the secondary vessel. I repeat, THE LID IS ON THE VESSEL.
It was NOT on the vessel when I got home. It was across the room. Most of the beer was still in the barrel. MOST. A small, but distressingly significant, volume had painted itself so the ceiling, taking with it krausen and chunks of semi-fermented banana. Another clean up job ensued, this time quite a bit harder as ceiling are a bit less friendly to clean than a floor. Et tu, gravity?
But I still bottled it anyway, and after a few months it was quite nice.
But I never brewed again.