Random MySQL Row...
I see that may be a big problem with a lot of items.

Code MySQL:

So lets say you do, this:
Wouldn't this be a problem if you had ID's like 1, 2, 3, 4, 7, 9, 12 -- You are missing some?
Code MySQL:
SELECT 
     id 
FROM 
     items 
WHERE id >= (
     SELECT FLOOR( MAX(id) * RAND()) 
     FROM items
 ) 
ORDER BY 
     id 
LIMIT 1;