Through out the game you can unlock transformations. There are some used by all and some that are race only. Some of the transformations are unlocked by using a certain race.

Unlockable	How to unlock
Future Super Saiyan	Complete the last story mission after the credits with any character.
Giant Form	Complete "Namekian Awakening!" in Guru's House by reaching Lv35 and talking to Piccolo, then Nail, then Dende, and Piccolo again. Must be a Namek.
Kaioken (x1/x3/x20)	Complete the Ultimate Finish in Parallel Quest 8 Invade Earth with any character.
Potential Unleashed	Complete the first 5 promotion exams in Conton City with a Z Rank. Then complete the Super-Rank Exam. Not restricted to any class.
Power Pole Pro	Unlock and complete the Great Saiyaman missions until unlocked. Must be an Earthling.
Purification	In Buu's House, feed Majin Buu enough food to create 3 family members, then talk to Majin Buu. Must be a Majin.
Super Saiyan (1/2/3)	Complete "Saiyan Awakening!" in Capsule Corporation at Lv40 and talking to Vegeta, then Bulma, then Kid Trunks, and lastly Vegeta. Must be a Saiyan.
Super Saiyan God Super Saiyan	Reach lvl 90 or higher and max out friendship with Whis. Note:If you want to max out Whis, you should probably wear Lord Beerus' Clothes.
Super Vegeta (1/2)	Complete the final mission against Vegeta in Capsule Corporation at Lv60. Must be a Saiyan.
Turn Golden	Complete Frieza's Spaceship Quest 18 The Omnipotent Frieza. Then talk to Cooler and Frieza once. Complete the next quest. Frieza race only.