Some accidents that I hope should happen to you and might give a pretty nice results!
I have written a tip about having light leaks on 120 film and said that this technique won’t look good in 35mm even if it is not planned. But I discovered that there is a chance on how your 35mm shots can get artful light leaks. However, this may not count as a technique and could actually damage your cameras or totally over expose your shots.
Anyway, it happened to me when my holga35 fell out of my jacket. I had nearly finished the roll and it just fell on the ground on a sunny day. The camera back sprang open and I immediately tried to closed it to save some of my shots from being exposed. I almost thought I lost the contents of the roll, rewinded it anyways and sent it to the lab. Seeing the results, on some of the shots, you can see the silhouettes of the sprockets and gave a nice effect on my photos, it worked!
So again: this is NOT a technique, it is an accident with results I like!