Have you observed the tumbling ARGOS satellite, or others that are noteworthy?
I just watched a pass of it over my location, with an impressive brightening and fading due to its slow tumble (roughly 30-45 seconds between consecutive maximum brightness periods, sorry so vague, I didn't think to time the period). Based on the limiting magnitude of the nearby stars, I would estimate it peaked at about magnitude +1.5 and faded to fainter than +4.0 (my limiting magnitude in that region of the sky tonight, not sure how faint it actually got, but I did lose sight of it) before regaining sight of it and its return to around +1.5.
It reminded me of an observation about 11 years ago, when I saw my first tumbling satellite (I believed it to be Raduga 33, but sites like heavens-above weren't available to me at the time), which really ignited my passion for satellite viewing.
Does anyone have any other recommendations for tumbling payloads that fluctuate in apparent magnitude so much?