CI High Interest Savings ETF (CSAV.TO)

Good place to park your money, and fees are low. 

Not much different from a money market fund, except the quality of the underlying securities might be a bit higher in a MM fund.

Very popular. Exposure to money markets of the various banks in Canada. Risk of rates retreating is always a risk, as these will be very responsive to whatever the current rate of interest is. Other than that, doesn't see significant risk.
 
There's always the credit risk of the underlying banks that are providing the yield that these ETFs are buying. Pretty safe, as credit ratings of major Canadian banks are pretty high and seem stable. Reasonable MER at 0.14%.