There are extended safeties, extended slide locks, extended mag release, extended triggers, beavertail grip safeties, magazines, titanium firing pin, oversized mag well, and solid guide rods. All of these are pretty much "drop-in" parts.
With some gunsmithing; a match grade barrel, match bushing, adjustable rear sights, front sights, 4-finger spring, target sear, and skeleton hammer.
This is only a partial list. Get a Brownell's catalog and you'll go crazy.