The man who makes it, doesnt want it. The man who has it, doesnt use it. And the man who uses it, doesnt know it.
http://kids.niehs.nih.gov/rd1.htm
coffin
The answer to this riddle is "coffin." Now, let me break down how we arrived at this answer.
The riddle states that the man who makes it doesn't want it. This suggests that the subject is something that is created, but the creator doesn't have a desire or use for it. Following this clue, we can eliminate various options like a cake (the baker usually wants it) or money (the printer usually wants it).
Moving on, the riddle states that the man who has it doesn't use it. This implies that the subject is something that is possessed by someone, yet they don't utilize it. Continuing from our previous eliminations, we can further narrow down our options.
Finally, the riddle mentions that the man who uses it doesn't know it. This suggests that the subject is used by someone who is unaware or unknowing of it. Considering our previous deductions, we come to the conclusion that a coffin fits all the criteria.
The person who makes the coffin (the carpenter) doesn't want it. The person who has the coffin (the deceased) doesn't use it. And the person who uses the coffin (the pallbearers) doesn't know they are carrying it.