The first bitcoin wallet software was Bitcoin-QT, which was a Bitcoin client as well. You can still download and run the very first binaries: https://bitcointalk.org/index.php?topic=68121.0. In 2011, MultiBit was launched, which was very popular at that time. Then, Electrum which probably one of the most used. Later, in 2012, Armory.

You should move this to the Wallet Software board.