This, I do a potato salad with olive oil, lemon juice or white wine vinegar, a bit of mustard, a bit of garlic, it's lush. You can also do it with potatoes that haven't quite cooled and they soak it all up (unlike if you did that with mayo which would go a bit claggy if it came into contact with warm potatoes!)
I also do a spicy coleslaw with an oil based dressing - red cabbage, carrot, apple, spring onions, olive oil, lemon/lime/vinegar (pick one as the acid element for the dressing) and a good splurge of tabasco or sriracha