Two years ago, I would have said my stash of Solly 916's and STH16 steel bindings. But I've been pretty happy with a couple of pairs of STH2 16's, so I wouldn't search for steel. I'd replace them all with STH2 16's.
My favorite piece of equipment, by far, is my boot set-up. Particularly the BD foam liners. I'd have another pair foamed in a minute. My boot fitter works with every liner out there, skis in BD's himself {he's a former French team guy}, and he convinced me that they would be PERFECT for me. He was right.
Wouldn't be too hung up on skis, as there are so many good skis out there. I would buy another pair of 180cm Head i.speeds for my cheater category, and new or newly leftover would be fine. I've spent a lot of days on many in that category, and I wouldn't change, though others would work. And in the hard to replace category, though they get limited use, a 196cm first generation Bodacious search would happen. Love that ski, in the right place, right day. I could probably be very happy with a newer generation 193cm, though. I may actually end up with both. But if my roof box ripped off the roof and was run over by a couple of semi's, I'd be looking for some 196cm's.
I'd have to do some testing to come up with the best choice in a sub 90mm ski, and roughly a 100mm. Right now it's a 184cm Monster 88, and a 187cm 2015 Bonafide. So many skis in those size slots........and good ones.
I also have a pair of older 184cm Stocki Stormrider XL's, that are now the early season and late season rockers. They still ski pretty darn well, and they have a lot of soul. I'll miss them when they give out.