Fairweather Friend
Used for friends who are with you in good times but forget you when problems arise.
Face Like Thunder
When someone is very angry or upset about something, he has a face like thunder
Flash In The Pan
Something which remains the center of attraction or is very noticeable but for a very short time. Basically its used for celebrities who raise to high fame with one hit and then are forgotten.
From Missouri
This means the person requires strong evidence before he believes anything.
Fly in the ointment
When something spoils the whole enjoyment we say its the fly in the ointment.
Fat Cat
This idiom is used for people who are wealthy and thus enjoy high status and influential position in the society.
Feather Your Own Nest
When some one uses his or her position for a personal gain, this idiom is used.
Feathers Fly
When people are very angry and start fighting or arguing we use this idiom.