In Ontario, the only prohibitions on full freedom within your will are that you cannot cut out someone who is financially dependent on you, and you cannot prevent a spouse from what they would be entitled to if you had separated the day before your death.
If you truly want to leave nothing to your spouse, you need to be aware of the fact that they can challenge the will based on their rights under the Family Law Act, putting your estate into lengthy and costly litigation. If you want to go this route, you should think about first getting a domestic contract in place to prevent the danger of a will challenge after you are gone.
