I've used many things over the years and still tend to stick with smaller objects. Sharpies were always a fave, now they make much larger ones. The other day I was at the dollar store in the toy dept (great place to hunt 'toys) picked up a water squirter (the kind that sort of looks like a piston syringe, worked great for enemas) a 'bubble nightstick' (looks like a cop nightstick about 18" long and filled w/ soap solution. It works for me as a dildo. and the solution made a decent sse diluted. Of course i'd had an oil enema beforehand so it came in handy.
A young female clerk asked if she could help me, i asked her if they had sharpies, she handed me an extra large one out of the restocking basket she just happened to be carrying. She asked if there was anything else I needed help with (if she only knew. "um yes, I'd like you to show me how to insert this Sharpie please ;-P ")
Another interesting homemade object was the veggie plug/nozzle made using a zucchini or cucumber half, using a pen, or metal rod and pushing it through the middle to create a channel, inserting an enema hose with small nozzle into the cut end and presto you have an extra large nozzle that is biodegradable and recyclable (on the compost heap not for family dinner please - "mom, this squash tastes like shit" )
oh yes, the dollar store also has $1 vibrating toothbrushes, complete w/ battery. Makes a cheap, disposable vibrator. I usually break off the head and customize it to suit my mood.