the cookie is dry and bland. I spit it on the floor.

I release a deadly virus in the home of the next user.

I run to walmart to get the vaccine.

I line the next users house with C-4, and detonate it in his sleep.

i dont sleep.

i sabotage a plane that the next user is flying by adding acid to hydraulic lines, these lines control the plane and he loses control.

However, I was using an experimental hydraulic fluid that was strongly alkaline. All your acid did was to neutralize the pH. As a result, I don't lose control of the plane,and I land it safely.

I sabotage the next user's car to detonate a hydrogen bomb if the person starts it, or if it is moved or towed. Also, the hydrogen bomb and its triggering mechanisms are not broken, missing components, or otherwise defective.

I use all the poop to fertalize my food garden. (I dont see how that was lethal...)

I stab the next person 37 times in the chest.

I pull my suit off to reveal the triple layers of kevlar underneath.

I fire the next person into intergalactic space. With a giant relativistic cannon and a wormhole.

I am an unstable atom called tritium. I am trapped in the doorbell system until I decay into a helium-3 atom, at which point I escape by sliding between other atoms due to my decreased size.

I poured liquid helium on the next user, before pouring molten iron on them.