Mandarin wonderin'

It has long been a recurring, even a stereotype joke in numerous sitcoms and movies that a non-native speaker of Mandarin (or other dialects of Chinese, perhaps) gets into an awkward situation through incorrect reproduction of vowel tones.

It would be great if someone provided a few real-life examples of phrases where the change of tone may totally change the meaning. It would be even greater if that were something innocent turning into something really embarrassing :)

Xie xie in advance :)