I have an old Optimus CD34000 from the early 90's that I love, it has a bright overall sound signature that delivers lots of detail but isn't weak on bass. It also has a tendency to sound bigger than it is; the sound opens up a lot and offers a good amount of transparency. It's a lot like a pair of Grados if you can relate to that. It's one of the well-known older players, Radio Shack of all places sold it back in the day; Optimus was their in-house brand at the time and they got really lucky with the design I guess. The main reason people liked them so much though was because it offered a digital out so you can use it as a CD transport.
It doesn't offer anti-skip or built in rechargeable batteries, as meithkiller said not many older players offer either of those features. I use rechargeable AA's, it takes four of them and runs for about 5-6 hours on a charge, so you'll definitely want to keep a fully charged set ready for when it goes dead. Some of the successors to the CD3400 offered anti-skip but didn't sound anywhere near as good.Here's
a review from Stereophile's online archives.
I also know that someone here at Head-Fi, I think it was Eagle_Driver, did a roundup review of all the old hi-fi PCDP's... try a search to find that one.