In fact many techniques were seemed too mchh stupid to work but when the rankings changed they did. The irony is that they would works just long enough for you to think you had beaten google.What "black hat" SEO tactic did you once think would fail but actually ended up working? And how long did it last before it stopped being effective?
Actually, a redirect or parasite page method "that worked for months" IS a successful BH method. Once your testing shows it to be effective for X months before Google detects it, bake it into the cake by cycling a similar page the same way for X -1 months, then rinse and re-do. One key to using black hat nowadays is to have an exit plan or recycle process scheduled into each tactic. The goal is not to permanently beat Google, but to structure things so by the time it's catching up, you've already switched to something else.One tactic I did not expect to work was using aggressive expired domain redirects. Surprisingly, it gave the site a noticeable ranking boost. The results were strong at first and came pretty quickly. However, the effect only lasted for a few months. Eventually, Google caught on and the redirects lost most of their value.