If you hit a rock with a shovel or an axe, money will fall out.
If you see a ray of light coming out of the ground, dig that spot up, and busy $1000 inside, a money tree will soon grow.
If you water 100 plants, someone will give you a very special reward.
If you purchase enough things from your regular store, they'll upgrade to a better store.
If you eat a whole watermelon, you can spit the seeds out like Bullet Seed.