I push the previous owner off the hill.

My hill.

Waits until the owner will go to the toilet (everyone have to sooner or later), then run on the hill.

MY HILL

put a chocolate cake at the bottom of the hill... everyone likes chocolate cake.

MY HILL!

I recite the ingredients to that cake, making everyone go after the previous owner.

MY HILL!

P.S. Portal Reference.

I detonate the explosives.

MY CRATER.

I decloak my Dead Ringer and backstab the previous owner with Your Eternal Reward before shooting him with the L'etranger for good measure. I then tip my Familiar Fez and announce...

We all knew it is MY HILL!!!

I make a $100 bill into a paper airplane, throw it, to be chased by the previous owner.

MY HILL!

I will point my finger to the previous owner and yell "BANG!" resulting into a heavy taunt kill.

MY HILL!

I declare Exterminatus on the hill, and it is reduced to a smoldering crater by an orbital barrage.

MY Crater!!!

Bucky says:
I make a $100 bill into a paper airplane, throw it, to be chased by the previous owner.

MY HILL!

Major but understandable miscalculation on your part. I don't chase after every dollar I see.

i start singing, and make you all run away.

MY HILL!