There's no way I could get 10 but to try:
1.Manda:he had his own attitude and demanded sacrifices from Orochimaru for usage. He was making Kabuto twerk in fear, in the end,he ended up being more of a demon then any tailed beasts lol
2.Kakashis dogs:, obviously a more humble one, but they're generally pretty useful
3. Shingami/Death God: Just ridiculously cool concept of sealing the two people and making them fight forever(slight point off for never seeing it though)
4:Enma: just generally cool
5:The Toads: I don't have a preference, they're all okay, I guess
Danzo and Hanzo have good summons as well, but they don't really do anything/have a personality, so idk.
I wonder why Obito and Madara never had summoning animals, btw?