Perfect rhymes:
* endix (a suffix used in some words)
* sex (a word that can be considered vulgar in some contexts)
Near rhymes (slant rhymes):
* endix (the suffix is pronounced differently, but sounds similar)
* decks (a word with a similar sound, but not a perfect rhyme)
* flex (a word with a similar sound, but not a perfect rhyme)
Words that rhyme in specific contexts:
* indexes (the plural form of index)
* appendixes (the plural form of appendix)
The best rhyme for you will depend on the context of your writing or speech.