If you drive a motor vehicle you have to buy gas so might as well benefit. I usually buy my gas in multiples of $3 from Esso to maximize point activity. As previously stated:
Ex. $50 transaction = 16 Aeroplan miles (3:1) + Earn 2/$1 on AMEX card is another 100 miles for a total of 116 Aeroplan miles for $50.

I recently found some Christmas ESSO Gift cards which include a separate card for 5 cent off 100 litres. I bought $700 (7 X $100) which gave me 1,400 Aeroplan points as I used my AMEX card. As I use the gift cards I get 3:1 again from ESSO and I save 5 cents a litre so you have to do the math in your head while pumping to maximize the multiple of $3! With fuel at 93.5 cents a litre in my area, every little bit helps.

25% bonus well I guess Lottery tickets, perhaps a phone card and maybe car wash as most things are priced too high! I will actually need to spend a few minutes in the store looking at what is the best value for a $12 purchase.