I have always been wary of vibrating butt plugs, unsure as to whether or not I would enjoy vibration in my ass.  Then Extreme Restraints sent me the Medium Trinity Silicone Vibrating Butt Plug and I was hooked!  I tried the medium, but if you are looking for a beginning or more advanced butt plug, there are small and large sizes to suit your needs.  The small, medium, and large plugs have widths of 1.25", 1.5", and 2" respectively.  The tapered design allows for easy and comfortable insertion, slowly warming you up to the widest point.  As this is made of ABS (a thermoplastic) and silicone, you'll want to use water-based lube with this plug.  The plug is a little bit more stiff than other plugs that I have that are 100% silicone but I was okay with this, as I love metal and glass toys.
 
The bullet vibe easily slides out so I was able to boil the plug prior to first use.  Upon insertion this felt very similar to other favorite butt plugs I own.  Now that I knew I liked the way the plug itself felt, I was ready to start vibrating.  The bullet vibe includes the three required tab batteries so you can start vibrating your ass right away - a good thing for an instant gratifier like me!  I reached down, gave the bullet vibe top a little turn and felt wonderful waves of vibration in my ass, as well as around my anus.  I was an immediate convert to the world of vibrating butt plugs.  This will also be the first plug I reach for when I'm going to enjoy partnered sex, as I imagine a penetrating partner would thoroughly enjoy the vibration.  And if not, it's easy enough to turn it off for static use.
 
The medium plug is currently $19.95 at Extreme Restraints, a great price for a versatile and fun butt plug.