I've been playing more handheld games recently as the quick-fix/on-the-go style is really handy. There have been many games come and go for me but most of them don't stick for more than one short sitting.
The internet is loaded with 'best of' lists but I wondered what your favourite handheld games of all time are, and why you like them.
Any device and any generation, including iOS and Android. I need inspiration.