In France, walnut oil is used all the time in salads - a classic French dressing consists of Dijon mustard, one part red wine vinegar to 3 parts walnut oil, seasalt and freshly ground pepper. Over there it's always so delicious, mostly because the oil is freshly pressed. On this side of the pond, it's usually imported and often already long in the tooth by the time it gets to your grocer's shelf.
But you can now order it fresh from LaNogalera, the brand produced by three walnut farms in Santa Barbara County, California. It's stunning. Use it raw, as it has a low burn tolerance and just gets bitter when cooked. It's made for fresh eating any where you are using olive oil: tossed with salad, pasta, in pesto, on steamed asparagus or roasted fish.