Best:
Razorback:
If you really think about it, the Razorback is actually a bit overpowered. Think about it. There are lots of snipers who stay with their team, with lots of them being in Highlander. If you're a spy, there are many problems with a sniper using the Razorback. If the sniper is with his team and you try to kill him with a revolver, most of the time you might not even kill him because his teammates will probably notice and kill you quickly. If you try to get him with the Ambassador, the same thing will probably happen, but the thing is that if you go for a headshot, you could two shot him, but only if he hasn't been overhealed, which medics should be doing to the entire team. Also, another problem is that some snipers have great muscle memory and can quickscope you right away, so if you shoot him with a revolver, there is a small window of opportunity for the sniper to headshot you. Snipers like to use the Razorback in competitive because they are very high priority targets, seeing how they can take out key classes like medics very easily. The Razorback denies spy's ability to take them out quickly with one backstab.
Scattergun:
This is definitely tying as Scout's best Combat Primary. Basically, anything that operates similarly to this, ie The Back Scatter and Baby Face's Blaster are about equal, and also the Soda Popper, which operates differently, but has a faster reload speed to make up for the Force-A-Nature's biggest weakness, and also has Hype. The Scattergun. Deals 100 damage at melee range, and has 6 shots. You have the potential to kill a heavy in less than 2 seconds. It has a fast reload with a nice ammo reserve with the biggest clip of the scatterguns. The spread is also a bit small for deadlier meat shots.
Bazaar Bargain:
With a high enough headcount, it's basically a hitscan huntsman.
Kunai:
Just nab a backstab and you're officially the strongest person on your team.
You can get an overheal even higher than a stock soldier. How is this not higher?
Got an enginner protecting a sentry and your reactions are slow? No problem the overheal would save you from the sentry's shots and give you time to sap it
Worst:
Quick-Fix:
The quick fix may not have over heal and a good über, but it is the fastest healer, and makes the medic match the speed of the heal target, which makes it useless since all medi-guns benefit from it, it doesn't save you from a fully headshot from a sniper while ubered either.