Oldest: Technics SL-P230 CD player. Never a moment's trouble out of this unit. It can go head-to-head with the much better known Rotel RCD-855 and cost considerably less. Bought in it February, 1989. Has a headphone jack and volume control, and powers my AKG K601 and Beyerdynamic DT 880 headphones at my computer desk. An overlooked wonder and one of the first low cost CD players that really sounded good.
2nd oldest: Rotel RCD-855 CD player. It refuses to die. Has many years of hard use on it. Bought it in spring of 1991. The newer CD players sound only marginally better, like the Sony DVD/SACD player I bought in 2003.
I have Heathkit W5M mono amps from the early 60's due for a rebuild this winter, then they go into my home theater system to power my Polk RT5 speakers. They have been out of service since 2002, but will be the oldest audio gear of anything I have ever owned when they go back into service.