Yamaha DX7
I've had a module version of this synth (the TX7) for a while, because I love the sound of Yamaha FM - but I just never
use it, because there's no on-board editing facilities, and setting up a MIDI connection from a master keyboard to a module is just so much less immediate and hands-on than sitting down with one of my keyboard synths. So I've been keeping an eye out, and one turned up on Craigslist for a pretty good price (I got the keyboard, a soft case, a stand, both factory ROM cartridges, and the switch and swell pedals for a good deal less than I've seen bare units go for elsewhere!) There's minor cosmetic damage and it was dustier'n hell, but it's otherwise in good shape, and it works and sounds great

What a classic!