Yes, BOMBER is a Scrabble word!

Letter values in Scrabble US: B 3, O 1, M 3, B 3, E 1, R 1.

Is it a valid word?

BOMBER is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a military aircraft that drops bombs during flight
a person who plants bombs
a large sandwich made of a long crusty roll split lengthwise and filled with meats and cheese (and tomato and onion and lettuce and condiments); different names are used in different sections of the United States

Also: hero sandwich, cuban sandwich, italian sandwich, poor boy, submarine sandwich.