Schildbach wallet is a software, Bitcoin only wallet. It is also called "Bitcoin wallet". The wallet is open source and transparent, users can send and receive and send Bitcoin without KYC or signup. It has a handy Sweeping feature, which makes it easy to scan a private key and sweep a paper wallet/BTC voucher and transfer all funds out.
The wallet is light weight, not too large too download, Simple user interface but not the most flashy or beautiful. The wallet is easy to use but does not come with many feature other than sending and receiving $BTC. The worst feature of the wallet in my opinion is its Bitcoin widget that shows bitcoin balance.
Overall the wallet is used by many people, and has good customer support. Cryptocurrency is evolving past only Bitcoin though, so someone like me would only use Schildbach wallet as an alternative wallet.