Build wise I've done several King of Tones, 1981 DRV's, Lightspeeds, super basic stuff like that. I don't really build to sell though, it's just stuff for personal use that I get bored of most the time.
Production stuff, for whatever reason I'm always flipping through delays and reverbs. I've probably bought/sold/rebought both a Timeline and Bigsky half a dozen times now.
Close to that with El Cap as well. Probably had four or five DD5s and RV5s. A couple echo parks. God only knows how many DD20s over the years.
I've tried to convince myself to like the DD500 like 5 times before swearing it off for good (this time for real).
I've had each of the M-series (m5/m9/m13) a few times. I think I'm on my third or fourth HX Stomp (oddly enough, they've all been bought used and somehow I have always wound up with the blue finish one).
This is also probably my 4th time owning a CS12 power supply (I buy one, convince myself to downsize, then gradually start adding more stuff and...back again)
I used to use a ton of the disaster area midi controllers too. A couple of DMC2's/micros, probably 3-4 DMC3's, another 3-4 DMC4's, a DMC6 twice, DPC8ez, DPC5, smart clock....BUT now I've just used morningstar for the last few years and been pretty steady with it.
Anyhow I usually just get kinda bored with my rig every 12, 18 months or so and impulsively blow it all up to try new stuff and wind up pretty much back at the same place I started. Wash, rinse, repeat