msmtp is an SMTP client with a sendmail compatible interface. It can be used with Mutt and other MUAs. It forwards messages to an SMTP server which does the delivery. Features include various SMTP AUTH methods, TLS/SSL-encrypted connections (including support for client certificates), support for multiple accounts, DSN, and IPv6 support.
Suricata is an Intrusion Detection and Prevention (IDS/IPS) engine developed by the Open Information Security Foundation and its supporting vendors. The engine is multi-threaded and has native IPv6 support, file extraction capabilities, and many more features. It's capable of loading existing Snort rules and signatures, and supports many frontends through Barnyard2.
Gwyddion is a modular SPM (Scanning Probe Microsope) data visualization and analysis tool. It can be used for all most frequently used data processing operations including: leveling, false color plotting, shading, filtering, denoising, data editing, integral transforms, grain analysis, profile extraction, fractal analysis, and many more. The program is primarily focused on SPM data analysis (e.g. data obtained from AFM, STM, NSOM, and similar microscopes). However, it can also be used for analyzing SEM (scaning electron microscopy) data or any other 2D data.