Worst Mass Murders in US History (any weapon):
By no coincidence all of the worst mass murders in US history have been non-gun.
Non-Gun Mass Murders (worldwide):
By no means is this a complete list. I have focused on 2008, and NOT included the majority of terrorist attacks in recent times, most of which involve car bombs (London), attaché bombs on trains (Madrid), the Sarin gas attack in Tokyo, etc. (and in fact almost all modern terrorist attacks are done without guns for the reasons of efficiency stated above).
Arson, Stabbing Rampage in Seoul South Korea : 10/20/2008. 6 people dead, 5 from stabbing. 7 others wounded, 4 seriously. An angry man felt people “looked down on him.”
Anti-police stabbing spree in Shanghai, China: 7/2008. 6 Police Officers stabbed to death, 4 wounded. 28 year old man angry at police attacked a police station with a knife.
Akihabara Massacre, Chiyoda City, Tokyo, Japan: 6/8/2008. 7 people killed (3 struck by car, 4 by stabbing), many more injured. Man slammed into a crowd with his car, then jumped out and began stabbing people to death.
18 year old slashes 4 to death in Sitka, Alaska, US: 3/25/2008. 4 people killed. 18 year old (old enough to purchase a rifle over the counter) kills 4 people, related to him, with a 5 inch knife.
Stabbing Spree kills 2, Tsuchiura, Japan: 3/23/2008. 2 killed, 7 wounded. Man “just wanted to kill anyone.”
Stabbing spree wounds 41, 6 seriously in Berlin Train Station: 5/26/2006. 41 wounded, 6 seriously. Thankfully no one died in this attack, but not for lack of trying on the part of the drunk 16 year old.
4 killed in stabbing spree in London, UK: 9/2004. 4 killed, 2 wounded. Mentally ill man attacks mostly older people.
6 killed over Xbox dispute in Deltona, Florida, US: 8/6/2004. 6 killed. 4 men (all old enough to legally purchase firearms) bludgeon 6 people to death with baseball bats over purloined Xbox.
Daegu subway fire, Daegu, South Korea: 2/18/2003. 198 killed, 147 injured. A 56 year old unemployed taxi driver, dissatisfied with his medical treatment, sets fire to a crowded train.
Osaka School Massacre, Osaka Japan: 6/8/2001. 8 children dead, 13 other children and 2 teachers wounded. Committed by 37 year old former janitor armed with a kitchen knife.