Perfect Rhymes (same vowel sound and ending consonant sound):
* dull (this is a common, but not very exciting, rhyme)
* hull (this is a more specific word, referring to the outer shell of a ship)
Near Rhymes (same vowel sound, different ending consonant sound):
* full
* pull
* bull
Eye Rhymes (same spelling, different pronunciation):
* shoal (meaning a large number of fish)
* coal
Slant Rhymes (similar vowel sounds, different ending consonant sounds):
* tool
* rule
* school
The best choice will depend on the context of your rhyme.