So far, this glitch worked on my DW4 Hyper and DW5 (PS2 version). I actually got it from SoSZ, wonder if anyone here knows about it.
1. Play anything with a second player beside you (or you control the second controller with your feet, that's what I can do :D)
2. Have the 1st player equip the Shadow Harness and 2nd player equip the Red Hare Harness.
3. When the battle starts, have the 1st player go to the 2nd player and make them switch horses.
4. There is a glitch that if you are equipped with the Shadow Harness, any horse will have the same effect. In other words, stealing Red Hare with someone like Ma Chao will give you the most practical horse ever. And also, although 2nd player sacrifices his/her Red Hare, he/she gets to ride Shadow Runner, too…