I was thinking, since gun laws are getting more strict, especially in the European zone, that if criminals wanted to commit mass murder with those higher numbers, they would have to use common everyday items that anyone can buy. But assuming that guns are banned and explosives are basically off-limits too, since just making a bomb is a very skilled activity and is easy to trace and shutdown in a civilized country where people don’t really need 500 kg of ammonium nitrate or the chemicals to make it in such high quantities, you would have to use weapons that are much more basic and easy to access. This is where knives mainly come in, as they tend to be the weapon of choice in most countries with stricter gun laws. In the other thread where I talked about mass stabbings, I mentioned 9/11, which killed 2,977 people and injured over 33,000 others. They used highly unusual weapons to commit the attack, such as utility knives, multitools and stolen airplanes. It was what lead to increased security measures at airports so that such an event wouldn’t happen anytime in the future. Then you also have fire. One of the plans the hijackers discussed during their planning phase was sabotaging a nuclear facility, likely by detonating a bomb outside a power plant to cause smelly air and acid rain. Basically a dirty bomb. What one could do instead is to simply buy a slingshot, an incendiary device and a 50 cent lighter from Wal-Mart to start bush fires everywhere during the summer. This would be just as effective as a truck bomb.
Then you also have car-ramming rampages, among other weapons used for amok attacks.