When I was younger I had a whole coffee can full of marbles I would insert 1 at a time and leave them for hours, In high school I worked in a gift shop stocking shelves, We had polished stone eggs, While doing inventory I found a full case un accounted for. It took me months to get a full dozen in me. The most intense thing I have ever had was with a Dom top who use to play with my hole a couple times a week. We were doing some strict bondage and he was sticking all sorts of things in my ass. After a couple hours of playing he wrapped his already large cock with 2 layers of thick rope. He put a couple of magnum condoms over it and fucked me. It was amazing but man I was sore for days after that.
A few other things..
3in dia steel ball bearing
sat on a ball hitch while giving a blow job
3 beer cans
shop vac hose
pool balls
cell phone