Commercials
Watching television has benefits in "Pokemeon Ruby Version." Once you have seen the commercial for Lilycove Department Store, you get a discount on your next purchase. Viewing the commercial for Slateport City Energy Guy and Mauville Game Corner means reduced prices on energy products and better prizes, respectively.
Time Trick
Your allotted time in the Safari Zone is based on the number of steps you take rather than a clock. To get around this, use your bike and hold "B" to use the hop trick. Hopping does not count as steps, and therefore, your time is unlimited.
Resurrecting Pokemon
Head to the Sandstorm in Route 111. A Claw fossil and Root Fossil can be found to the far right. Collect one of these and take it to the President's Office in Rustboro City. Head into the room full of scientists and talk to the one in the bottom right corner. Go outside, wander around and then return to the scientist in about half a minute. He will give you the living version of your Pokemon fossil.
Mystery Event
Head to Petalburg City after defeating the Elite Four. Talk to the man on the computer and enter "Mystery Event Is Excited" when he asks you for a profile. Save the game and turn your Game Boy off and on; the Mystery Event feature will be available.
Rayquaza
Once you have beaten the Pokemon League, you can find the Pokemon Rayquaza. Get on your bike and head to the far right side of Pacifidlog Town, and then straight up. Go through the gap that will lead you to sky pillar to find the Rayquaza.
Wynaut Egg
Look for a woman standing next to a hot spring in Lavaridge Town. Talk to her, and she will tell you about an egg that she can't raise. Accept the egg from her, and it will turn into a Wynaut Pokemon.