"The Delivery Man"

Rocks-Off recommends "The Delivery Man" for shared spaces, and that's the useful part: a custom motor tuned to rumble low rather than buzz high, in a body 16 centimetres long and a little over 3 centimetres across.

If you live with people, or with thin walls, quiet matters more than power on paper. Ten settings, one button, 120 grams, so it stays easy to hold at an angle for a while. Ten centimetres go in, and the tapered tip suits external pressure just as well.

Three hours of charging over a USB cable gives about three hours of play, and it's fully waterproof, so the shower is fine. Use water based lubricant. The run time is the limitation: three hours is average rather than generous, so charge it before an evening rather than after. Rocks-Off guarantees it for two years.