Mix 1 gallon of bleach with 1/2 gallon of ammonia. DO NOT BREATHE FUMES, serve through vents. You have a deadly gas. BAN BLEACH AND AMMONIA!
Take 1 jar extra creamy peanut butter, heat and dilute with peanut oil until a "slime" consistency. Use in places that have large gatherings... Bonus if you decide to mix in a few dozen bee stingers, double allergen "chemical weapon," BAN ALL PEANUT PRODUCTS AND BEES!
Those are two that I came up with while smoking a cigarette. The objects are easier to obtain than guns, and don't need to be concealed (actually, you SHOULD NOT conceal them) or explained away in a stop.
Anyone with an internet connection, ingenuity, a rudimentary understanding of collegiate biology (which can also be attained via the internet) can weaponize almost any viral strain or bacteria... It's actually a fairly novel process (except the self-exposure danger.) Weaponizing an influenza virus or a bacteria would be quite simple, building an antibiotic resistant strain of the plague wouldn't be impossible, and would only require 1 clean room/area, time, and a more advanced understanding of biology ...
Guns don't kill people, or make them more dangerous. Two of the most prolific serial killers targeted children, each had over 200 bodies, and never used a gun*. Criminals will ALWAYS have access to firearms, even the criminally insane (a gun dealer doesn't run a psych. eval. prior to selling unlicensed firearms.) If attaining guns becomes too difficult (take Japan, N. Ireland, or Palestine for example) and you still want to fuck shit up, you can always make poison gas and release it on a rail, you can build car bombs and set them off in crowded underground/bus exchanges, or build a bomb-vest/IUD and blow up a coffee shop/school/checkpoint. Yeah, guns are causing most mass deaths in the US right now, but stripping them from people won't make anyone safer. Criminals and the insane will still have access to them, and intelligent psychopaths will still develop weapons for the incompetent (take Raytheon and G.W. Bush for example.)
*The Butcher of Ecuador is no longer in prison, his whereabouts were unknown last I heard about him. He served 18 years (That was the MAXIMUM sentence allowed)for the 200+ confirmed (bodies found) kills he had. It's estimated that his ACTUAL body count could be upwards of 600. He didn't believe in firearms.
EDIT: Sucks about that bus driver and kid... Too bad we had to win that "cold war" with Russia. Had we kept government asylums for the criminally insane, and improved them as we've improved jails and prisons, this person might not have killed that bus driver, and wouldn't be hiding in his fort with a kid and a gun.
I do realize the irony of my supporting asylums - I would be in one myself, but, we'd have about 10 less mass shootings over the past 3 years (that I've seen/heard about.) and, I'm smarter than hell, I'd either be the madman running the asylum, or I'd have "checked myself out" as it were.