The word "un-stimulating" suggests something that is bland or uninteresting. However, there are many antonyms that can be used to describe something that is stimulating or exciting. These include terms such as stimulating, electrifying, arousing, thrilling, exhilarating, exciting, invigorating, inspiring, motivating, and uplifting. These words describe sensations or experiences that are engaging and captivating, and can be used to describe anything from a thrilling adventure to an inspiring piece of art. Using these antonyms in appropriate contexts can help to make language more expressive and engaging, adding color and interest to written or spoken communication.