Hummmm, what an interesting and intriguing topic. I know I've forgotten a few, but the ones that come (cum?) to mind are:
1) My faithful 12 gallon Shop-Vac. It has a two and one eighth inch diameter hose opening, and is "perfect", and will be again, ...... later today.
2) My hand held shower head, on pulse. I love the name, shower "head". Got the cleanest cock in my zip code!
3) An orbital sander (without sandpaper!)
4) A large pillow filled with buckwheat (an organic orgasm)
5) Water jets in various hot tubs, alone and with others.
6) The bottom of a steering wheel, while making out with a girlfriend. Did this a lot in high school.
7) The corners, edges, and sides, of various furniture.
An all time "favorite" was a girlfriend's long, luxuriously thick, extremely soft and super curly, hair, and no, I never came in it. It was her idea, and I'll always love her for it.
9) This same girlfriend's panties, with and without her watching me, and even joining me. Whew!
10) Another girlfriend's knee, as I knelt in front of the chair she was sitting on and "humped" while we kissed, forever! Made my dog envious!
11) A huge Webster's Dictionary in my lap, sitting at a table in a school library.
12) Against the back of a display case while exchanging sexy innuendos with an "older woman" during a Summer job in college. I climaxed, and she leaned in smiling, and asked, "Better?"
I know there has to a few more, but all I can think about is that shop-Vac calling me from another room. Loud, but satisfying. Sound familiar?