Are these all OK?
I had an experience I will never forget.
It was something I will never forget.
It was an experience like nothing.
It was an experience I will never forget.
It was an experience I didn't enjoy at all.
It was the most beautiful feeling of my life.
It was the most beautiful feeling I have ever had in my life.
This is the most beautiful feeling I have ever had in my life.

Question

Are these all OK?
I had an experience I will never forget.
   It was something I will never forget.
   It was an experience like nothing. 
   It was an experience I will never forget.
   It was an experience I didn't enjoy at all.
   It was the most beautiful feeling of my life.
   It was the most beautiful feeling I have ever had in my life.
   This is the most beautiful feeling I have ever had in my life.

Answer

The only one that does not work is, "It was an experience like nothing."
If you want to use that sentence, you will need to add to the end of it: "It was an experience like nothing I had ever felt before" or "It was an experience like no other." 
That would make more sense. Otherwise, you are saying that the experience had no feeling at all, when you really mean that there is no other feeling quite like it.

Answer

The last three are absolutely correct!

Answer

It was an experience like nothing.(this doesn't sound correct though technically it could be correct if you knew what nothing felt like)

Try....I had experienced nothing like it before.

The rest seem ok.

Answer

correct
correct
incorrect and I don't know what you're trying to say sorry
correct
It was an experience I didn't enjoy
For the last three they just don't sound right.Instead of beautiful I would use best.
"It was the best feeling of my life"
"It was the best feeling I had ever had in my life"