For example:
* Wow! That was an amazing performance.
* Oops! I dropped my keys.
* Help! I'm stuck!
However, if the interjection is used in a less emphatic way, a comma (,) may be used instead:
* Well, that was interesting.
* Oh, I didn't realize it was so late.
It's important to note that the punctuation used for an interjection depends on the context and the level of emphasis.