Well, as you know by now I love a lot of things. So remembering what I did 10 years will take come effort...there was this one event that I would like to repeat very soon.
Disassemble a pistol (Beretta), cleaning it and putting it back together. But the real challenge was to do it within a specific amount of time at which I failed. The process was sweat generating at the highest level but my natural born love for weapons made me wanting to do this more often.
That sounds cool @faustofraser!