Pentax/Brother PocketJet 3 Plus
You will often see the PocketJet 3 Plus printer listed under the brands of either Pentax or Brother, but they are the same thing. The PocketJet 3 Plus mobile printer is an interesting model because it is a thermal printer and therefore does not require ink cartridges. While it is nice to not need ink replacement, which is always very expensive in the long run, the trade-off is that the thermal print quality isn't quite as good nor as fast. On the plus side, thermal printing doesn't smudge like ink does. It prints at 300 dpi, but only up to 3 pages per minute, so it's pretty slow. Bluetooth, USB, and IrDA connectivity is supported, but no WiFi.
This neat little printer weighs just a little more than a pound, and it measures roughly 10 x 1 x 2 inches in size. It's so small that most people probably won't even realize it is a printer at first glance. Prices for this model vary greatly, but normally start around $300. While the upfront cost may seem higher, keep in mind that you won't ever have to buy ink for this type of printer. The only downside is that thermal printer paper costs more than regular paper.
Most reviews of this printer are generally average, meaning that people aren't too impressed by the print quality or the lack of speed. It is not recommended for users who plan to do a lot of printing, but who may occasionally need to print something on the go, such as a customer receipt.
(Image credits: Amazon.com)