Perfect rhymes:
* dowser (a person who uses a divining rod to find water or other resources)
* shower (a device that sprays water)
* tower (a tall structure)
* bower (a leafy shelter)
Near rhymes (slant rhymes):
* cower (to shrink back in fear)
* power (ability or strength)
* sour (having a sharp, unpleasant taste)
Let me know if you'd like more examples!