For my main work I tend to use the Mora Companion and Mora 106 in combination. The Companion is the most fantastic camp knife; it keeps an edge like no knife I’ve ever had and is fantastic for coarse work, particularly rough shaping and stripping bark.
The Mora 106 is arguably the best fine whittling knife available for a sensible budget. It’s great for detail, and will make short work of a decent piece of Ash or Yew. The Mora 120 has a shorter blade and is arguably better if you’re doing lots of very fine detail, but as an all-rounder I think you can’t beat the 106. It’s worth making a leather strop to keep the edge honed, but with a bit of care this blade will last you a helluva long time.
When I’m out and about, not on a specific whittling adventure but happy to take the opportunity should one present itself, I like to carry an Opinel No 8. It folds, locks, and keeps a great edge. I don’t really know what more to say about it, other than it’s by far the most handy and practical of my knives when out and about.
My last one is a medieval viking style knife that I picked up at a medieval fair. It’s made of good carbon steel, which took a while to get a good edge on, but has held it well ever since. As it’s not stainless I have to be careful to keep it particularly well oiled, but otherwise it’s solid, durable, and way more practical than it would first appear. I mainly use this when I’m at medieval events, as it’s the only one that really fits with the period.