The Powder Toy

Virus (It's a type of pathogen)

Glacier (Can be a source for a river)

Mod (requires coding)

Milky Way Galaxy (Another name for therocketeer)

Sun (What Mars orbits.)

However, I create a small black hole that lasts long enough to pull in all of the poo before it evaporates.   The next user is falling onto a neutron star, where they will be flattened and sprea...

However, I happen to be living so far into the future, that the Sun has already long since burned out.   I throw the next user into a wormhole, that leads into a universe where matter cannot exi...

Dropping them into a fusion reactor

Strange matter (This is also a form of matter, like antimatter)

Antimatter (Makes the largest explosions per volume of material)