To add:

/whois /who /whowas are critical for placing k-lines, akills, and
tracking down nick changers.
/mode being able to set usermodes... we have many non-standard usermodes
on DALnet. +g global, +y (to see who /whois's you), +c (to turn off or
on client connect/exit msg's), etc...
/links
/ping
/onotice (notice channel ops)
