There isn't really one specific "best", it all depends on what kind of edit you want to make, your technical skill and budget (or just pirate) If you are just trying to throw some clips together with a song Imovie would work great, its free and easy to use.
If you wanna do some more advanced stuff and you really wanna learn editing Final Cut Pro or Adobe Premiere, there used to be a really easy way to get adobe for free without downloading anything sketch but it sadly doesn't work anymore.