Kyosho Golds by a large margin. The ease of rebuilding, the consistently excellent damping action, the oil retention...I've opened several decades-old beat-up-looking Golds to find them still full of clean oil. I've rebuilt Platinums and I concur with Jeff on those. I was fortunate enough to get a set of Brimod shocks in a parts car lot from another member and polished them up really nice, they're beautiful...but honestly I don't think they could beat the Golds, either. I haven't found anything that went together that easily and worked that smoothly.
Worst shocks, also by Kyosho: the infamous red OEM shocks for the Optima and other cars. The silly thin plastic gaskets always breaking, the red shock collars always cracking, the need for a special tool just to disassemble them, and the constant leakage put them high on my "worst shocks" list...maybe at the top!
Golds even look great...when they're not gold.
