Tools without which I would not be the same man
Obviously, there are a lot more tools that one uses during the day, especially the little ones we never think about (hello, grep and openssl). These are just the ones I consistently find myself installing when starting from clean slates.
Infrastructure
Debian / Ubuntu
FreeBSD
nagios / zabbix
sysstat
haproxy
MySQL
PostgreSQL
KVM/qemu
lxc
Development
vim / ctags
mercurial
git / tig
screen
selenium
httperf
Sequel Pro
adminer
mininet
Management
yEd
Dropbox
Skype
iWork ($)
Google spreadsheets
Feng Office
Security
wiresharkngrep
socat
ratproxy
nikto
skipfish
netfilter
Interestingly, the only not free one among these is iWork.