My fall brassicas: broccoli, kohlrabi and cauliflower were fails because they never even got started. I dragged my feet and just didn't do them.
I have yet to have any real success at growing spinach, though I try every year. The plants never get very big or robust, whether they are spring plantings or fall plantings. They also seem to be a real target of pests!
Cucumbers were also pretty close to utter failures. Last year I was giving cukes away by the bagful and making jars and jars of refrigerator pickles. I have only grown the heirloom variety Double Yield and been very pleased with them. But alas, this year they produced a mere handful of cukes. With the cukes, I'm not at all sure what the problem was. Maybe it was just the location I chose for them.
That about covers my 2012 garden! I have missed mentioning a few successes like my garlic and shallots, which did really well this year. And the garden's not finished yet; I have brussels sprouts yet to harvest and cool weather crops such as kale going strong. I am not done totalling the overall poundage yet, but I know I have harvested more than in 2011 so it will turn out to be my best garden to date, which is what I strive for each year: to improve the garden and to improve as a gardener. There is always more to learn and I can see that the importance of self-discipline is one of the lessons I am learning. I'm already looking forward to next year's garden!