Any protein that dries out quickly in cooking is perfect for sous vide – I especially like rabbit which always turns out moist, as well as things like duck, quail, pigeon, pheasant breast, guinea fowl, and the already mentioned venison. For whatever reason I don’t like chicken done sous vide – I find it has an unpleasant sponginess. Some vegetables benefit – sweet potato doesn’t get gummy and okra doesn’t go slimy. Custards turn out silky if you don’t have success with traditional methods.
Of course you can’t make a true pan sauce. You can brown meat before or after sous-viding for flavour but you won’t get a long-developed fond in your pan, which means adapting a recipe. And you have to get your flavourings right from the start because you can’t adjust as you go, and you’re limited to what you can add just before serving. This can be tricky with any flavourings that need to cook, such as curry mixes and pastes, or flavours that magnify when cooked, such as bay.