no holds barred
是指不顾对方的面子和情绪，毫不迟疑地把自己的想法说出来。

例句:
"My wife and I had a real no holds barred talk last night about all the things wrong with our marriage."

比如说，一个美国朋友可能会对你说:“我和我的妻子昨晚可真是毫不留情地谈了一谈，把我们婚姻方面的所有问题不管三七二十一都说了出来。”

knee-slapper
意思就是"一个能让人笑得拍大腿的笑话"。
下面的例子是一个爸爸在说他的儿子:
My son likes to tell jokes, although he has no intention to become a comedian. Last week, at a party he told a couple of knee-slappers about Bush and Gorbachev. I was quite surprised at his talent. 我儿子喜欢讲笑话,虽然他没有意图想当一个相声演员。上星期,他在一次聚会上讲了两个有关布什和戈尔巴乔夫的笑话,笑的人们直拍大腿。真没想到他还有点天才。
显然,这位爸爸对儿子的才能没有充分的估计。