Go Vacation - Nintendo Wii

In the mountain resort of Go Vacation, you can choose between a Jeep (Off-Road Car), a horse, and a kayak; this trick is about the first two.
If your fellow player parks their jeep or horse near the water, you can push them into the water!

You can simply push a horse by walking into it, and if it falls into the water, it respawns (it goes back to the start).

There are various ways to get a jeep into the water, but using your own jeep is of course the fastest;
When a jeep ends up in the water, it sinks to the bottom, so you can see it (the water is not that deep) but you can't grab it.

If you want to annoy your fellow players, be sure to do this!

In every resort, there is a pathfinder, which means a secret route where there is often a treasure chest as well.
There are plenty of tip sites on the internet, but for these pathfinders, you can't find decent information anywhere, let alone in English! Here's a clear overview:

Marine Resort:
This is probably the toughest one in the game, as it requires the most effort.
The secret exit is located in the Off-Road Park, which is very large. On the map, head to the spot marked with a boat icon, if you've got the right one, you'll start on a pier. Of course, you'll need your Quad (ATV) because otherwise, you won't get far enough.
Once on the pier, you'll see a path going up on the left, follow that path, and at the fork, go left.
After the fork, you'll reach an open field with a wooden hut in the middle, just keep driving on the path you came from. After a short drive, you'll see a stone ramp, STOP! You'll need that ramp. When you're in front of the ramp, you'll see an opening in the rock wall to the right, with two cones on the edge, that's where you need to go.
So, reverse to get a run-up, and go OFF-CENTER over the ramp. If you do it right, you'll make it over the edge of the opening in the rock wall. Now just keep driving and ride into the hole in the ground.
You'll now receive the pathfinder star, and if you go left, you'll see a treasure chest in the water.

City Resort:
This one's a piece of cake; when you're on the mini-map on the right, you'll see a skate park with a tower of three UFOs above it. Go ALL the way down there, and ride over the colored tiles, then you'll get the pathfinder star.

Snow Resort:
This one's also a piece of cake; go to the top of the mountain, and head down. Keep hugging the left wall until you come to a small path. Follow that path, and do NOT go on the stone bridge you almost immediately encounter.
At the stone bridge, turn right (you'll get the pathfinder star along the way) and keep following that path, eventually, you'll reach a treasure chest.

Mountain Resort:
Go to the castle, and at the big gate, go left. Once you're past the castle itself, look to the right. You'll see platforms you can jump on. Follow those platforms until you're all the way on top of the tower.
There's a treasure chest there, and when you walk over to it, you'll receive the final pathfinder star.

Once you've earned enough stamps in the game Go Vacation, you'll eventually unlock the Villa Ground. When you head there, you'll spot a picnic table on your left-hand side. Next to it, you'll find a rather peculiar-looking ball. Toss this ball into the pond nearby, and watch as a UFO pays a visit to the Villa Ground!