No actual "firearm parts", if that's what you're asking. That includes all internal parts, obviously, but also magazines (and mag parts), grips, and sights.
It's not obvious if you're new to this stuff: The problem is actually exporting from the USA rather than importing to Canada. The US has tight controls over what they allow to leave the country. ITAR is what it's called, I think. You may ask "When was the last time you were stopped on the US side when coming back to Canada?" It's never happened to me, but I'm not ever going to spin that wheel.
As above, "accessories" like holsters, weaponlights, speedloaders and cleaning supplies are not subject to these restrictions (last time I checked!).