From HackerNews:
gnosis 14 hours ago | link
abcde — CD to mp3 ripper
apg — random password generator
base64 — better than uuencode
boxes — draw any kind of boxes around your text
bsdiff — binary differ
bspatch — binary patcher
bvi — binary vi (yet another hex editor)
ccx2 — console xmms2 client
clive — flash video downloader
dvipdfmx — dvi to pdf converter
enfuse — poor man’s HDR
get_flash_videos — yet another flash video downloader
glark — advanced grep
indent — code beautifier
lshw — list hardware configuration
mcurl — multiple part downloader using curl
mktemp — safely create temporary files and directories
msort — sort records in complex ways
netbrake — bandwidth limiter
od — octal dump
par — paragraph reformatter
par2 — archive verification and repair tool
ped — sed done right with perl
pinfo — color info reader
pipe.vim — make vim part of a unix pipe and allow it to
edit the pipe contents
pv — Pipe Viewer: a tool for monitoring
the progress of data through a pipe
pydf — pretty df (disk space viewer)
qmv — use your favorite editor to rename files
(part of renameutils)
qodem — modem program that can do serial, telnet, ssh,
zmodem, kermit, etc
rdiff-backup — like rsync, but can do incremental backups
recode — like dos2unix and unix2dos, but with many more encodings
recordmydesktop — make screencast videos
remark — great logfile colorizer (part of regex-markup)
rkhunter — find rootkit infections
rlwrap — add readline editing support to any command
safecopy — data recovery tool (better than dd)
sponge — soak up stdin and write to a file
(for things like pipeline editing)
sux — su while transferring X credentials
unbuffer — force flushing of stdout
upx — executable compressor
utimer — countdown timer and stopwatch
vared — edit shell variables (part of zsh)
watch — run a command multiple times and display the output
(with differences highlighted)
xdotool — simulate keyboard and mouse activity
xxd — hex dump
zargs — a version of xargs that makes the find command redundant
(part of zsh)
zed — very small and fast vi-like editor (part of zsh)
zrun — automatically uncompress arguments to command
More at: http://kkovacs.eu/cool-but-obscure-unix-tools