Whether you like it or not Yachiru will give you a nickname cuz she forget most people's name..
A few canon nickname that you should be aware of (Cheat sheet):
Zaraki Kenpachi - Ken-chan
Ayasegawa Yumichika - Yun Yun
Maderama Ikkaku - Baldy, Pachinko head, Cue Ball
Kuchiki Byakuya - Byakushi and Byakun
Masumoto Rangiku - Boobies
Toushirou Hitsugaya Snowball/Snowball-Taichou/ Captain Snowball
Nicknames so Far
NPCs
Her Golem - It switches between Batty and Eyeball.
The Yeti - Monkey/Saru
Characters:
Komui Lee- Switches Between Megane and Komu-chin
Ryuuichi - Ryuu-chan (and Kumagoro is Kuma-Kuma)
Shuuichi - Shuu-chan
Duo - Duo-chan
Lavi - Lavi/(Red?) Bunny-kun...if she ever over hears what Kanda calls Lavi
Roxas - None as of yet
Ace - Acey
Smoker- Smokey
Reever- Ree-chan/Lab Coat
Lambo Bovino - Broccoli Head
Dick Gumshoe - Gummy/Trenchcoat
Apollo Justice: Polly/Antenna
Bo Peep: Dolly/Dolly-chan
Roland: Ro-kun? Knight
America: (Glasses?)
Axel:Fireball/Pyro-kun
Namine: Nami/Nami-chan
Xion: Xi-chan or XiXi (Pronounce Shishi)
Hermione: Mi-chan/Book-chan
Chesire: Kitty!
Koromaru: Koro-wan (Wan is the japanese way of saying "Woof')
Yuuko: Has only talked to once (Possible?)
Fegland- (If/when they meet Eyebrows!)
Canada - (If/When they meet Invisible-kun)
Also, if there is a particular nickname that you want to be used feel free to comment or if you think up of a funny nickname you want her to call you muses comment here