Oh man, I'm sure I have a lot I can't even think of right now. The biggest one is the 50 ft 1/2'' immersion chiller that I stopped using - I now use my two stage counterflow and can chill a 5 gallon batch in about 7 minutes in one pass to the fermenter.
I also have two propane burners that I've just kept even after moving to electric.
I have some drip trays, oxygen tank setup with victor regulator and 2 micron stone, and a paintball co2 tank filler that I don't use anymore.
things that I still use on an infrequent basis: beergun, bench capper (with a bucket of caps), spunding valves, and I'm sure others.
I will say that I have a whole slew of spare parts that I keep on hand just in case that I don't use very often, but I am very happy to have them on hand when I need them - mostly 1/2'' stainless fittings, but also 1/4'' flare fittings, garden hose fittings, camlock fittings, spare regulators, pressure gauges, 1/4'' valve, 1/2'' valves, o-rings galore - essentially every o-ring I would need in bulk.