Actually I dont think that some of app really change my life, but I most app what I need is: Mapy.cz (it has very good maps for Czech republic, and for last year it have maps for a lot of other counties - for me its better than google maps). And second app what I really like to use is my app Easy selfie - just because of one functionality - tap to take a photo. And I dont use it for making selfies, just for regular photos. I like it much more than built-in photo app, even it has much less functionality (but for me - less is more).