Wilcox

The ~ keyboard character is called a Wilcox. The proper position for the Wilcox is at the end of a short sentence, usually in a text or email. It denotes an end of sentence terminator where it needs more than a full stop but is not quite worthy of an exclamation mark.

Full stop - You did a great job.
Wilcox - You did a really great job~
Exclamation mark - Wow, you did great!