This is a sketch of the Rube Goldberg contraption that opens the gate to the house. The steps are writen out below.
Thanks to Shaz from the messageboard for the contribution!

1) Bowling ball rolls down slight drop in railing to...
2) Bucket which pulls...
3) Rod which closes bellows..
4) Blowing up balloon...
5) Which is popped by pin...
6) Scaring rabbit who runs on treadmill....
7) Pulling boot which kicks football...
8) Onto paddle wheel...
9) Opening valve...
10)Allowing water pressure to turn sprinkler...
11)Which wraps up string to open gate!

Discuss this here.