Cake Wallet is an option to consider (https://cakewallet.com/).  Available on mobile and some desktop platforms (only Linux and MacOS currently), and it claims to be open source code (github).  Passed 8 of 10 tests in security audits on walletscrutiny.com, but they apparently had some trouble fully validating reproduced builds from the source code.  The wallet handles XMR, BTC, and LTC currencies - but I suggest you only use the wallet for moderate amounts for daily use and not for long-term storage.