Our really dislike saying "It" even though that's what the little being is until he/she develops. I wanted to be silly and use "zygote" but DH said it makes him think of a goat, which makes him think the kiddo will come out with a goatee (which would be horrible if we have a girl)....
DH wants to use poppy seed, but it's too overused. I want something different that could be used for a girl or a boy.
***ETA*** Thank you Audreesmama, we have chosen Ziggy. DH liked it because of Ziggy Stardust (David Bowie)!
Thanks everyone for all the great replies. I guess poppy seed wasn't as overused as I thought...
My brother and I teased each other by calling the other "Nugget" when we were young - so my dad has nicknamed our baby "Lil Nugget". But my husband has christened her "Belly Nut" because he didn't like Belly Bean either!
Incidently, you can default to "She" terminology early on because everyone starts out as a female until the gender really develops...that's why men have nipples! :-)