Things that aren't in the scriptures or in any church handbook, but none-the-less a certain group of LDS members firmly believe in them and occasionally judge or persecute those who do not adhere to them. This isn't new. You may remember that in D&C a large group of members started teaching that to be a good member you needed to be a vegetarian, until Joseph Smith put a stop to that none sense.

In modern days, I have heard that in order to be a "good" Mormon, you must:
Abstain from caffeinated sodas, (possibly hot chocolate if you want to be very righteous).
Cheer for BYU and hate the University of Utah
Not watch any sports on Sunday and possibly wear your church clothes all day Sunday even after you get home from church
Never use the word "sucks"
Avoid any TV shows with adult humor including "The Simpsons," "Friends," "Three's Company," "Modern Family" (pro-gay agenda), as well as all R rated movies and PG 13 Movies.
Not use playing cards and avoid investing in the stock market because it is a "game of chance."
Vote conservative republican on all issues.

Let me know if there are any others I should add.