Any and all Aneros toys. Subtle g-spot dildos that are solid, like glass. Going further, realistic dildos but I didn't get into those for years after having hands-free prostate orgasms from Aneros toys.
About 10 years ago I used an Aneros... Only did that once. I was standing in the bathroom and finally figured it out.... My legs buckled as I came and nearly knocked myself out. It took me a good hour to clean the cum I sprayed all over the place.