Positive meanings：
积极的意思：
She is a peach to work with.
她是一个很好的工作伙伴。
He is a rose of loveliness.
他很可爱。
He was the No.1 seed in the table-tennis championship.
他在乒乓球锦标赛里是一号种子选手。
Yemen lost the flower of its youth in the war.
也门在战争中失去了很多优秀青年。

Negative meanings：
消极的意思
My friend was stuck with a lemon on the dance floor.
我们有在舞池上被个不好的人缠上了。
This car he sold me is a total lemon!
他卖给我的这个车也太次了吧！
I don't wanna be gooseberry between you two.
我不要做你们两个人的电灯泡。