If you want to store any altcoins then you can use Metamusk Browser Extension. You can hold more than one HUGE amount of altcoins here. But if you want to hold Bitcoin then Electrum wallet will be best for you. Because it is considered a Bitcoin secure wallet.

You haven't mentioned here what kind of coins you want to hold and which blogchain they are on.  Due to this it is not possible to give you an accurate information.  You should have mentioned this. Then you would get a proper answer