Can you think of a perfect synonym?

Ok, this is harder than it sounds. I'm off work sick, and I'm amusing myself by trying to think of words that have the same meaning, usage, AND connotation. For example, hard and difficult would not count, because hard is generally less formal. I might consider lonesome and lonely to count, but perhaps lonesome has a more Romantic/poetic connotation. If anyone has any candidates, please post them! 10 points for the best answer! Thanks for indulging me...