I'm at the moment using the firewall built into Avira Premium Security Suite.
Online Armor free Firewall
Outpost free Firewall
PC Tools Firewall
Comodo Firewall
Sunbelt Kerio Firewall
ZoneAlarm free Firewall
Private Firewall
Windows Firewall
I use a Commercial Firewall (Built inside Antivirus etc.)
I dont use a Firewall
I'm at the moment using the firewall built into Avira Premium Security Suite.