Banana (the artificial flavour, I actually quite like the healthy ‘ice-cream’ that’s just frozen banana blended up with some dark chocolate chips) or bubblegum.
My son also once insisted on a fake orange flavoured one once in a theme park that was absolutely disgusting (I think it’s the only time I’ve ever thrown an ice cream away).
I love rum and raisin ice cream (there’s a restaurant near us that makes it’s own and it is delicious) and other controversial flavours like coffee, lemon, and salted caramel.
I also had a matcha/white chocolate one the other day that was lovely (and matcha always comes up on the threads about horrible foods that are inexplicably popular)
My absolute favourite is a dark chocolate sorbet with either candied orange or candied ginger, both of which horrify my husband!