It would be great if a food was added to a "favourites" group when you add it to your diary, and when you search for food the favourites appear at the top.

This would make it easier to find foods when there are many foods with the same name and different calorie values. E.g. searching for Hellman's mayonnaise returns so many results and I have to go through and compare nutritional values with the ones on my jar.

the recent / most used lists should help with that as they will only have the one that you've used before having verified, but if it's been a month since you used that mayo, or you have only used it for lunch before by default it doesn't show in your dinner list.

that can be changed though

Pick your platform

Website
food > food diary > pick a meal
on the "add food to (meal selected) page there is a search box and RIGHT below it
"or add favorites for (meal selected)
click that (meal selected) and change to the only other option "all meals"

Android / iPad / iPhone
http://www.myfitnesspal.com/help/faq/75-can-i-see-my-most-used-items-across-all-of-my-meals-not-just-the-meal-i-am-adding-a-food-to

Blackberry
http://www.myfitnesspal.com/help/faq/120-can-i-see-my-most-used-items-across-all-of-my-meals-not-just-the-meal-i-am-adding-a-food-to

Windows Phone
http://www.myfitnesspal.com/help/faq/212-can-i-see-my-frequent-items-across-all-of-my-meals-not-just-the-meal-i-am-adding-a-food-to