If anyone has kids, a spouse, etc. for which you want to convey a little of your love for fish, I think betta fish are a great introduction.
I got my wife a betta fish for Christmas a long time ago. He made it almost six years, and was a fantastic pet. During the summer, she kept him on the island in the kitchen. When he was hungry, he would swim sideways to where you were moving and show off his fish plumage. When you finally brought your face to the side of his aquarium, he would turn and swim straight up to your face. She would then feed him.
I finally had to replace her betta this Christmas. The pet stores now have a much greater variety of species (or perhaps hybrids?), some of which look almost as fancy as piscine peacocks!
Her new fish has now learned similar behaviors to her old betta, and is pretty entertaining for a pet that you cannot cuddle. He is very fancy and we have never had to treat for any of the various aquarium fish maladies. (I don't know if that is just luck, or if they are just hardy fish.)
Just throwing ideas out there for the rest of the pondmeisters.
However, IMO if you had a 6 y.o. granddaughter and got her a good one, then you might retain your "favorite grandparent" title even longer!
![grin grin](/images/graemlins/default/grin.gif)