Are you referring to a plug adapter, and not a device that includes a transformer (for converting voltage)? Most devices these days, laptop adapters, shavers, hair dryers, etc., are worldwide voltage (110v - 240v), so in the vast majority of instances, one would not need a device that includes a transformer, thus saving considerably on cost and bulk.

If you fall into this camp, then my advice would be to get a kit, something like this and further minimize on bulk by only taking the plugs you need:

http://www.amazon.com/Lenmar-Interna...travel+adapter

Note that I am not specifically endorsing this particular brand or store, but just providing an example of what I am suggesting.

I am personally not a big fan of the all-in-one units. Sure, they keep everything in one place, but I find them bulky and occasionally difficult if not impossible to use in some countries that like to recess their outlets.