My friend has PDA device with a slick dictionary program. He can transfer files to his computer and auto-generate ANKI cards and he wants with it. He can also save words in various lists, one of which is called HARD MOFOs.
I have my own list kind of like this, made of my daily class mistakes, which I will blog about more in the future, but have mentioned a couple of times recently. There are many words that I have no problem with after input, and they are easily recalled when they show up. Then there are the sticklers. Really basic words that have been haunting me for as long as I have studied Japanese (about 3.5 years now). They show up every day in the deck. Sometimes I finally get over them with Heisig mnemonics (I remember things better when I have the kanji down) or other odd memory stories.
Alex shared some good ideas lately. I find his sentence thing works well, when I have the time to do it.