I go inside the LHC tunnel. Other than an increased radiation level due to synchrotron radiation, nothing happens because the actual proton beams are inside a sealed vacuum pipe.

 

The next user is trapped very deep underground, and is beng killed by the extreme heat.

I am trapped deep underground....in a life-supporting heatproof bunker.

_____________________________________________________________

The next user is eating biochemical weapons.

I got stronger like the Hulk.

-------------------------------------

I rip below user to 999 pieces.

I am a critical mass of plutonium. I simply start a nuclear reaction and kill you via acute radiation poisoning before you could do anything.

 

The next user is a normal human who has been exposed to a lethal amount of both thallium and arsenic trioxide.

I'm wearing a gas mask. (btw your name refers to Uranium 238 LOL)

_________________________

The next user is in a pool of water while a completely ordinary human being...suddenly a giant block of Caesium is forced into the pool from beneath the pool so it doesn't burn up in the air and violently explodes right below you.

You haven't defined how much caesium. I eat a tiny amount, not enough to cause any damage.

The next user is eating half a kilogram of caesium very fast.

There is not that much cesium around. Therefore nothing happens.

 

The next user is eating five grams of francium. If the explosive reaction with water does not kill you, the tremendous heat released from its radioactive decay will, by explosively vaporizing the material and setting nearby things on fire.