Always include models manually, if not in the controller / shell:
$this->Deal = ClassRegistry::init('Deal');
and then
$this->Deal->create();
Advantage: you allow Cake to be downloaded and run the model for you, so if you have done this before, it will try to reuse it.
EDIT: for the sake of completeness, inside the controller / shell you can just do
$this->loadModel('Deal'); $this->Deal->create();
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