I'm glad F for Fake was mentioned as a DIY film - for me, it can never get mentioned enough.
But if you have that top 5, please don't overlook The Apostle. Robert Duvall wrote the script in the 1980's and spent years getting turned down by studios before eventually financing the film with $4million of his own money, producing, directing, starring and doing a duet with Emmy Lou Harris for the soundtrack! His acting performance is incredible.