μTorrent (also called microTorrent or uTorrent, short for "µT" or "uT") is a freeware BitTorrent download client, written in C++. It is the most widely used BitTorrent client now, outside China (where XunLei is more popular and has the has the largest number of users in the world).
PPSSPP (short for PlayStation Portable Simulator Suitable for Playing Portably) is a cross-platform and open-source emulator originally created by Henrik Rydgård (AKA: hrydgard, one of the main members in the development team of the renowned NGC/Wii emulator - Dolphin) from Sweden, in 2012. It can perfectly run the vast majority of PSP games, supports Windows, Linux, Mac OX, Android, iOS and many other mainstream computer and mobile device operating system.
AutoCAD is undoubtedly the most popular and powerful CAD modeling software. But as a commercial software, it is really, really expensive. FreeCAD is a free, open-source, cross-platform and general-purpose 3D CAx (CAD, CAM, CAE), PLM modeling tool specially designed for home user/hobbyist, experienced CAD user, programmer or educator.
It was originally written in C++ by Christophe Dumez (from France) in 2006 when he was a student. Now it's maintained by worldwide volunteers on their spare time. qBittorrent is a free, open-source and cross-platform BitTorrent client (torrent file downloader) with nice UI based on Qt and built-in search engines.
Navicat Premium is an award-winning universal database managing tool that is enough to meet professional database developers' all requirements. In particular, for newcomers to database servers, it is also quite easy to learn and use.
Aegisub (successor of the original SubStation Alpha and Sabbu) is a free, open-source and cross-platform advanced subtitles creating & modifying tool. Recognized as an industry standard of all subtitle editors, it is widely used by numerous subtitle groups and subtitling fans for the subtitling and translation of concert, OP, PV, TV, animation and some other aspects like video post-production.