In this post I will write about the best mobile crypto wallet.
In my opinion and experience it is a Jaxx mobile wallet.
Jaxx wallet is also available for many platforms (desktop and mobile), more details on Jaxx official website.

Update, February, 2022.
You can use mentioned Jaxx Liberty or some other mobile wallet but the best security you will get with hardware wallet. Recently I have bought Ledger Nano X and I use it connected with desktop Ledger Live official wallet but also there is an option to use it connected via bluetooth to mobile phone. You need to install Ledger Live mobile application. That means you can manage your crypto account and make transactions with mobile phone connected to Ledger hardware wallet. New device Ledger Nano X have a battery. If you dont have experience with hardware wallet I recommend to read my post How to use a hardware wallet.
Update, January, 2019.
There is a new Jaxx wallet version called Jaxx Liberty. All important features such as that private keys stays on your mobile device are the same. Jaxx team added some graphic improvements and cool widgets: crypto news, market. Also news is that coins exchange via ShapeShift is not supported anymore on Jaxx Blockhain wallet but is supported on new Jaxx Liberty wallet. I have tested Jaxx Liberty wallet and is working fine. Here are some screenshots and app you can search on official website or in app market via your mobile phone. Be aware that for crypto exchange ( if you want to convert BTC to ETH for example ) via ShapeShift – you need to register ShapeShift account and give some your info.
My recommend is to use on mobile phone. If you are using on PC I recommend to have installed some good antivirus program.
In general mobile apps are more secured in compare with apps on PC, especially if you are using Apple mobile phone like me.
I am using Jaxx wallet on my Iphone 6 mobile phone more than 1 year without any problems.
Why Jaxx Blockchain wallet?
Jaxx supports many cryptocurrencies and crypto exchange via ShapeShift. That means you can exchange from one to other cryptocurrency without needs to use crypto exchange or trade sites. Big advantage is that private keys are stored on mobile phone, not on network. App is very simple to use.
First you can choose which cryptocurrencies you want to use in your wallet – you can change (add / remove) anytime.

On “tools” section you can view private keys, make wallet backup and some other things.
You can setup your security PIN on “settings” section.
Be aware: never share your private keys!
To receive crypto just copy your crypto address – click on symbol to the right and send it to your sender.

Exchange is very simple: just choose cryptocurrencies and amount, then click “exchange” button.

You will be asked to confirm transaction and enter your PIN.
For a few minutes you will receive amount in other cryptocurrency.

Jaxx is a very simple multi cryptocurrency wallet, quite secured especially if you are using on mobile phone (my strongly recommend). We can also say that is an offline crypto wallet because private keys are not stored on network. If you choose to use it my recommend is to follow Jaxx team on twitter to get news about new features, updates, potential issues.
However for large amounts I recommend to use some hardware wallet.
I hope that this information is useful for you.
If you have any questions or doubts feel free to ask via comments.