My power amp: the Nakamichi PA-7, designed by the legendary Nelson Pass. This features the "Stasis" design found in the more expensive Threshold amps. (And on closer examination, the internal build, and the schematic, are nearly identical to the Threshold "S" series power amplifiers from the same era.) ToneAudio has a nice piece on this amp, and there are good examples of it on eBay.
Dahlquist DQ-10, a 5-way design, became the first widely sold time-aligned loudspeaker. Each driver was mounted on its own baffle and positioned so each voice coil was aligned in the same plane, assuring the sound from each arrived at your ear at the same time. The result is an incredibly realistic sense of 3D stereo imaging. It set off a wave of various time aligned speaker designs, which many saw as a design fad, one that quickly faded. Time alignment is still controversial.
Bryston Limited: 3BSST² Dual-Channel (Stereo) Amplifier The Bryston 3B is still in production in the latest SST2 iteration. These amplifiers just get better and better. Their 20 year warranty makes them unique in the world of audio.