I take one gas mask and run, leaving the the clean-up to somebody braver than I.

He came, he puked, he left.

*Leaves a full jerrycan and matches.*

Accidentally knock over the jerry can and light a match as I am still leaping away, which starts a fire.

Leave the puke from the last user for the next user in a zip-lock bag in case it can stop the fire

I extinguish the fire with a frosty stare and leave the zip-locked retch to the next user in case of, well, another fire. Now off to act maturely in front of real people.

v I disregard what was left and leave an Eisbock for the next user to post.

Drinks the Eisbock (thank you).

Leaves a "Summer breeze". (Sorry)

I open a window to let the wind out and leave an incoming whiff of all things green and luscious for the next user.

{enjoys the fresh air}

v [leaves a ray of Texas sunshine]

I endure the heat long enough to bury the sunshine in my backyard, then collapse from heat-exhaustion and the landing hurts extra bad because of the heavy sunburning.

I reanimate MichaelD.965 to scold him before sending him home. Leaving dead bodies isn't acceptable even if it is your own.
I leave a paddling pool filled with fresh moutain water along with an assorted collection of ice cold alcoholic and non-alcoholic beverages.

V [ I leave all but one bottle of the ice-cold alcoholic libations along with a picnic basket full of goodies which Yogi Bear was close to making off with a few moments ago. ]

Leaves leafs.

I come with a leaf-blower and ineffectively blow them around for hours, just because I like to terrorize everybody who comes along with the terrible noise.

I leave the complaints about my noise pollution to the next user.

Of course, they fall on deaf ears. (I think you can figure out what caused the deafness.)

(Note: Not actually deaf, but pretending to be one because I think it's funny.)

I leave a Healing Potion +1, +2 against dragons, for the next user.

I take care of that and take the potion to the dragon living in my neighbourhood...don't want to risk such a potion falling into the hands of self-declared "heroes" coming to attack the dragon. The dragon is grateful and rewards me handsomely from his hoard.
As I leave, I hear how he's barbecuing and devouring a group of foolish knights. I guess that potion could have been useful to those fools, lol.

I leave a crystal dagger the dragon gave me to the next user.