These five items in Team Fortress 2 are not completely useless, only more inferior compared to the others. When you pick the Razorback, you can no longer use two reliable weapons, the Jarate and Sub-Machine Gun. Replacing the Shotgun with a Flare Gun or Sandvich means the Heavy and Pyro can have a harder time fighting in close quarters. There are basically better items than these five, that is why they are the worst ones in TF 2.
The irony behind the Sandvich is that you think it's suppose to save you from dying, when it can easily get you killed as well. Why? Because of the significant consequence for just eating a sandwich. The cost can be greater than the gain when using the Sandvich.
While you're busy munching on one, you're immobile and unable to attack until you finish it. The worst part is the Heavy making loud noises while eating, easily giving away his position if anyone hears him. If you haven't used a Sandvich, go give it a try, and when you think you're safe while eating, an enemy suddenly pops up from somewhere and you're helpless to defend yourself.
The best way to survive while eating a Sandvich is to go some place you're absolutely sure no enemy is around, and there are not many spots like that in this game. There is little point to the Sandvich when a Heavy usually tags along with a Medic who can bring him back to full health in seconds.
The Medic's Blutsauger will give three extra health for every ammo that hits an enemy, but he can already regenerate one health per second by just standing around. If a Medic must regain health, just stay in an area with no enemies nearby and regenerate. It's safer than attacking enemies head on with the Blutsauger, a situation that puts the Medic at a greater risk of getting hurt.
The team will count on you to heal so you won't be using your weapons most of the time. The Syringe Gun is a better weapon when you need to attack, since it can deliver critical shots unlike the Blutsauger.