Synonyms:
boom, bonanza, gold_rush, gravy, godsend, manna_from_heaven, windfall, bunce
Meaning: a sudden happening that brings good fortune (as a sudden opportunity to make money); "the demand for testing has created a boom for those unregulated laboratories where boxes of specimen jars are processed like an assembly line"
Usage examples
An assassin, what a godsend!
The hard ice of this slope is a godsend and both grottoes will be ideal for their purposes.