I use this string from time to time when testing applications. It verifies/tests the following areas:
- Unicode (the "лежт" part)
- SQL injection (the single and double-quotes)
- HTML formatting (the "<" sign etc)
The string is: <a '% &x " лежт F8E5>
Embarrassingly this was the result after testing it on one of my personal websites :)

5e35e766-e47d-4a42-bcd4-b1e49f7c9868|1|5.0