This compact MIDI keyboard is great for musicians on-the-go or casual players who just want a fun distraction. The best thing about it is that it's powered by USB, so there are no leads to leave behind.
It works great with Garageband, so if you've got a Mac you just plug it in.
A key feature of the MPK Mini is the built-in drum pad and arpeggiator, as it gives you all sorts of options. The syth-action mini keys are also handy, as they're designed to save space.