Putty.exe for connecting to gear.
Packet-tracer and capture commands in ASA. Packet-tracer alone is enough reason to dump FWSM and migrate to ASA.
Wireshark for looking at the captures.
3CDaemon (lightweight FTP/syslog server).
Grep (via GnuWin32).
Boson subnet/wildcard calculator
Venti caramel frappaccino. I make no firewall changes in the morning until after I've had one.