I had an issue with squirrels getting into the eaves and attic of my house. they had chewed holes through the cedar facia boards.
I tried a number of various repellants to discourage them, but nothing really worked. They were actually tearing up the fiberglass insulation to make nests, so i don't know what it would take to really irritate a squirrel.
I finally bought a live trap. I used a peanut butter and bird seed mixture as bait. Each morning I would load the trap and each evening I would release a trapped squirrel into the woods west of my house. The advice I found on the web suggested that the squirrels have to be released at least 10 miles away so that they don't find their way back. After a couple
You are never going to build a catapult that will fling them ten miles away!

After a few weeks of trapping the squirrels, we had the soffit and facia redone in aluminum. they have not come back in since.