OpenBSD user, in no particular order, definitely missing some stuff: pdksh (OpenBSD) or oksh (Linux/MacOS), su, unix/posix utils (man (most important), find (second most important), apropos, awk, grep, df, du, dd, ed, etc), mg, openssh, got, heirloom-doctools/troff, bc-gh (bc calculator with a bunch of extensions), xclip, xdotool, xeyes (very important), yt-dlp (youtube-dl seems dead these days), some C compiler (clang/gcc), httpd, opensmtp, ffmpeg, libressl/openssl, pf, tmux (I prefer to use my window manager, but if I'm in tty or need to retain a shell session, tmux is useful), ping, ifconfig, traceroute, netstat, nc/netcat, unwind (or other dns server like unbound)