I have a Korg SG-1D as a master controller I still use everyday (knock on wood). It use to be the best sampled piano...12 bit! in fact, Bruce Horsby rented it from me for a concert in Milwaukee. Purchased in 1991.
I use Eric Perching's Distorted Reality sounds still (Oil Can Bow is in my current project!), those started in Akai sampler mode, migrated to Giga Studio and now Kontakt. Must of gotten those in the early 90's
Looking around the studio I have Minimus 7 speakers from Radio Schack. Those must be the oldest I have. I like to compose to them because 1) I'm use to them 2) No ear fatigue!!. But i just use them to check mixes nowdays. Those I believe are circa 1986.
I'll keep checking for more..I'm sure there other relecs I'm just not thinking of.
Oh yea, what about Sonar, starting with Cakewalk around 1990!