opensshd
pgp
nmap (cant live without it, beats ping)
traceroute
iftop
rtorrent
telnet/netcat
http servers (they have thier uses)
pump, uhdcpc dhclient (life savers)
wpa_supplicant
those are my top 10, not in order. if i had the room i would add a netwrok daemon that configs the network on cable insertion but i cant remeber the names of any