The Smith manoeuvre

Unlike in the U.S., the interests on your primary residence's mortgage are not tax deductible in Canada. 

The Smith Manoeuvre - from Fraser Smith - consists in borrowing against the equity built in your house to invest in income producing vehicles. The interests can be written off from your taxes.

This way, you can gradually restructure the largest non-deductible debt of one's lifetime (a mortgage) into a deductible investment loan.