30 years old: HP-11C calculator, Kenwood audio amp, Bose speakers, AKAI tape deck are all still running after 30 years, although they don't get much use, the tape deck especially.
25 years old: Yamaha PAC-921 guitar. Had to replace a potentiometer but it works perfectly, and with decent maintenance will probably never fail. There are tons of people with older electrics
And the current champion, which I don't think anyone's mentioned: my Dad's hand me down 60-year-old slide rule. Still works, and I threaten my students with it occasionally