Can you start a new sentence with the word whatever?

'Whatever' may be classified as slightly too informal for a serious essay, but it is not necessarily going against grammatical convention to use it as the start of a sentence. For example you could say:

• Whatever the cost, the general and his army needed to hold their ground.

It could also be an interesting way to incorporate some attitude into a character's speech:

• 'Whatever!' she yelled insolently, 'I love him and you can't do anything to stop us being together!'