Use 'something else' to show that you find someone or something astonishing or exceptional. His performance was something else, I've never seen anything like it!
Pro Tip 2/3
Beyond Average
The phrase suggests someone or something far surpasses what's normal or expected. Her intelligence is something else, far better than any student I've taught.
Pro Tip 3/3
Positive Emphasis
Usually carries a positive connotation and can subtly express respect or admiration. Your work ethic is something else, I really admire that.