The Legend of Zelda: Majora's Mask/Secrets

Takuri
This is that really annoying bird that flies at you and steals your stuff (remember, if anything important gets stolen from you, either go buy it back at the Curiosity Shop or play the Song of Time). If you feel apprehensive about facing this thief-bird, put on the Stone Mask so he doesn't try to steal from you, but it's easier to hit him when he's flying at you instead of in random circles. Pull out your bow and shoot Takuri till he dies (I like to use Light Arrows). When his body drifts to the ground, it will yield a huge rupee…200 big ones! Now just head through the loading zone into Milk Road and back and do it all again! Have fun.

Clock Town
Even though the Takuri rupees make all other get-rich-quick schemes obsolete, there are other ways to get relatively quick money:

East Clock Town There are two treasure chests each containing Silver Rupees: One of them is down in the Bomber's hideout. Down the ramp and to the left when you get to the water. Pull yourself out of the water at the end and blast the wall with either a bomb, bombchu or the Blast Mask (use your shield while you blast to protect yourself from harm). Open the chest to receive a Silver Rupee (100). When you come out of the Bomber's hideout, hang a left and run along the left wall, hopping over gaps (use the nest outside Honey and Darling's game place as a jump-off). When you get to the far corner, turn right and head to the chest. Open it to receive your reward. You can also play at Honey and Darling's game place on the First and Second Days to win a Purple Rupee (50) if you score a Perfect. On the Final Day you get a Piece of Heart If you didn't score a Perfect on both the First and Second Days, you can also win a Purple Rupee on the Final Day. After you get the Piece of Heart, you can win money all three days.

North Clock Town
Pretty much all there is to do here is the Deku game. As a Deku Scrub, burrow into the flower next to the Great Fairy's cave and launch yourself into the fenced-in area. Drop down the hole and participate in the game. The object of the game is to collect all of the rupees by launching yourself out of the Deku Flowers onto other platforms…but you may not touch the ground. The prizes are the same as Honey and Darling's. If you win the game on the First and Second Days, you get Purple Rupees and on the Final Day you get a Piece of Heart. After you win the Piece of Heart, all you'll get is money for winning all three days.

South Clock Town
On the Final Day, obtain the Land Title Deed from the Deku Scrub by trading him the Moon's Tear. Use that to fly to the platform with the chest on it (opposite the Clock Tower). Open that chest to receive a Purple Rupee. Alternately, use the hookshot.