Two Three tools for extracting information and/or manipulating large pgn files. Especially pgn-extract did impress me. From lichess I downloaded a file (213 GB!) for later training a NN. It took close to 12h on a single CPU but I was able to extract around 5 GB of games, filtering time control between 900 and 3600 seconds plus dividing the files into the ECO codes A – E.
(Update:) Someone asked for the uci-analyser, here you go: