No, you do not need to list your country of residence as a country you've visited, since you will be including the fact that you reside there in the part of your application where you give the details of your residence. In earlier versions of the application, the question was actually asked with somewhat more precision: "Have you travelled outside your country of residence, excluding to the UK, in the last 10 years?"
The application also asks how long you've lived at your current residence. If you've lived in Tunisia for less than 10 years, and you visited Tunisia from an earlier country of residence within the last 10 years, then you should include that. Similarly, if you've moved your residence several times in the last ten years, then you may want to consider including those movements.
The important thing is to avoid giving the visa officer any impression that you are concealing anything. If you've lived in Tunisia for more than 10 years, there's certainly no reason to list Tunisia as a country you've "visited." If, on the other hand, including Tunisia in your list helps to present a clearer picture of your travel history then you should include it.