I like GRAPESEED OIL Vegenaise. I think it tastes better than regular mayonnaise, really great! It's a little hard to find, though...
One time I found an organic sunflower seed oil mayonnaise that was runnier than regular mayonnaise but had a good taste. Can't remember the brand.
Those are the "healthiest" mayonnaises that I have found. Still not convinced either one is actually good. So I use the Vegenaise only occasionally. I'm thinking I'll just start making my own, with egg yolks and olive oil, as someone mentioned. That would be the best. But since you asked about store-bought, that's my answer.