There are two unique horses that have special effects in the game: the Persian Mare and Moon Child. Both are unlocked by completing special missions in Survival Mode on 71F. If you have enough money, start from 51F and play until you reach 71F. Unlock the Persian Mare and Moon Child by performing the corresponding tasks:
Persian Mare Play the "Transport Rescue" mission on 71F, although it becomes available only when you complete the regular "Medicine Hunt" mission. On every floor, focus on protecting the Supply Captain, especially on the last two floors. On the first floor, rescue the Supply Captain by defeating the four Raiders attacking him. On the second floor, defeat Magoroku Saika to pass. On the third floor, you will face a couple of Raiders and Vagabonds. Avoid them and defeat Magoichi Saika. On the fourth floor, you will face Vagabonds and Miscreants. Avoid them and defeat Okuni. Once she is defeated, she will return. When you defeat her, she will appear once again along with Magoichi. You will need to defeat them and prevent them from killing the Supply Captain. On the fifth and final floor, defeat Kotaro Fuma. When you defeat him, Hideyoshi, along with Nene, Mitsunari Ishida, and Sakon Shima will appear and charge the Supply Captain. You must quickly defeat them before they kill the Supply Captain. After defeating them, the Persian Mare will become available in the shop.
Moon Child Play the "Shopkeeper's Escort" mission on 71F. On the first floor, kill all the Miscreants on the floor. On the second floor, the Supply Captain will move and stop randomly. When he stops, find some Musou Wine. It can be found in any container. On the third floor, defeat four Raiders to make way for the Supply Captain to escape. On the fourth floor, defeat the Marauder. On the fifth and final floor, you will face Tadakatsu Honda, Ina and Ginchiyo Tachibana. You should defeat Tadakatsu first to make things easier, as he is very powerful. After defeating them, the Moon Child will become available in the shop.