Mayonnaise, cider vinegar, sugar, horseradish, celery seed. This is rather simple and when you make it it rests in the refrig. Then just before you serve, drain well. In spite of the mayo it's not a thick, heavy mayo style slaw dressing. Sometimes I'll add finely chopped onion and green pepper, sliced green onions and diced, seeded tomatoes to the mix.
Pans approach is a good one too and for a cooked dressing try using a poppyseed- rice vinegar, sugar, chopped shallots cooked then cooled and made into a vinaigrette with canola oil or maybe a warm bacon dressing- rendered sliced bacon with drippings, chopped shallots, cayenne pepper, flour (for the roux) cider vinegar, balsamic vinegar, sugar s&p to taste.
Then sometimes I'll just make an Italian dressing- red wine vinegar, olive oil, chopped garlic, fresh oregano, chopped red onion and add some honey for sweetness and toss the slaw in this.