The Mom & PopCorn shop will give you a free sample of just about anything in the store so you can "try before you buy". They have over 45 different flavors of popcorn, making it somewhat overwhelming to pick which flavor you want. So asking for a sample is a great way to decide which one(s) you like best. Their $1.25 snack size bags are an economical way to buy a small portion of several flavors, or they will mix different flavors in the same bag if you ask. My favorite flavor is "creamy dill".
They also have gourmet fudge, saltwater taffy, nostalgic candy in glass jars that can be bought by the pound, and other fun and tasty goodies.
The staff is very friendly and will go out of their way to make your visit fun and nostaglic. If you are in the downtown McKinney area, this is one stop you have to make!