The oldest fish I bought and actually raised would be my black skirt, who I've had almost a year now, but my oldest fish is my L-204 plec at 2 years old...
I used to have some 10-15 year old goldfish, but there was an incident and all but one died.
Currently, my oldest fish are my 3 female mollies, which are around 1.5-2 years old now. Raised them from the fry, so they are some of my favorite fish.
I would also have said my Black Moor, if I still had it, but I gave him away when he out-grew my tanks He would be about 2 years old now... and I wish I had him back, he would be a fine addition to my 75gal tank. Maybe some day I'll find another little one to raise