CyberChef: Countless en-/decodings, cryptographic ciphers, hashing, data formats,…
GoAccess: nginx/apache log analysis. Beautiful representation in terminal, HTML output (incl. graphs) also possible.
NetreSec NetworkMiner: Easily extract hosts, files, credentials,… from a PCAP file. Windows only!
Minimodem: A software audio modem.
Seatty: Receive RTTY, NAVTEX, HF-FAX (WEFAX), GMDSS DSC (HF and VHF) and NWR SAME via audio files.
Sonic Visualiser: Spectrograms FTW!
Stego Toolkit: Everything a stego challenge fan could wish for in a Docker container.