Do you have a favorite? Games? I am looking for two, one that counts as you squat and one that does something so you don't get calls when driving; I think it is for teens but I am sure it would be beneficial for adults as well.
Candy Crush was addicting for a while... I don't play games on my phone anymore. I only use it for the internet, phone calls, texts, travel-related apps, and financial-related apps.
SwiftKey is the most important thing I've downloaded/purchased by far. Totally worth the 2 bucks and probably 100x that. Other than that I've paid for Tapatalk, PowerAmp, Nova Launcher Pro and the Gameking and 3/5 Play modules of the videopoker.com app. All totally worth it. WhatsApp is 99 cents a year after the first year and a great app for international/group texting.
Funny timing for your post because Swiftkey just announced this morning they are dropping their fee and offering the app for free. Also I didn't realize Whatsapp was charging a subscription fee now. I downloaded it a looong time ago and its always been free for me, they must have added the subscription fee later. Its by far the best messaging app, so much faster and more reliable than the native iPhone SMS system. This is such a wide-ranging question because there are so many different types of apps. For wifi security though I have finally started using Tunnel Bear as a VPN when I'm on a public network and its fast and works great. I bought that game Blek recently which is a pretty fun way to waste time, but I've only played it for a few mins here and there. I've also recently been playing this free game 2048 lately, so far I haven't been able to finish it. What I'd really like is an app that helps me get rid of other apps. I have so many on my phone now and I probably don't use 90% of them but when I look at them I think I should keep them on because I feel like I might use them some day. So an app that slowly just deletes apps I never use without me knowing would be cool.
I have an excellent one called Aw, Craps! Excellent way to learn the game and try out different strategies. You can even use finger swipe to "throw" the dice. Gives you an idea of the touch required.
I got an email this morning that they were giving me a free premium theme pack on the updated SwiftKey, guess they're going to get by on selling themes now and the free pack is how they're repaying the people that have actually purchased it in the past. I just got Whatsapp like six months ago, so the 99 cent fee after the first year was made apparent to me, perhaps you're lucky and grandfathered in for life! It is a great app, I have a group of 17 old college rugby friends in one group and we just talk shit, share pictures and videos, get into heated debates, etc. nearly every day. Much better than Facebook for keeping those guys in my life, IMO. Try SDMaid for the cleaning you were talking about if you're on Android. It has a 'graveyard' search function that gets rid of residuals from long uinstalled apps. I think it also tells you the last time you used an app, so whilst not automated will help you decide what to get rid of manually.