Similar: This implies a strong resemblance but not absolute sameness.
Exact: This is very close to identical, emphasizing precise and complete sameness.
Duplicate: This refers to a copy made from an original.
Alike: This is a broader term suggesting general resemblance.
Equivalent: This focuses on being functionally equal, not necessarily physically the same.
Mirror: This emphasizes complete reflection, as in a mirror image.
Ultimately, the best synonym for "identical" depends on the particular situation and what aspect of sameness you want to emphasize.