Egg vibrators generally have a fairly quiet vibration. This, in conjunction with their discreet shape, makes them ideal travel and public play companions.
The Lovense Lush 3 is an example of an egg vibrator
While egg vibrators are commonly used anally in some adult videos, they lack a flared base - which makes them unsafe for anal use. Users attempting to insert one into the anus should take care, as it may be difficult to extract unless it comes with a cord especially attached for anal use. An alternative could be pressing the vibrator against the base of a butt plug.