No. As DavidGrove mentioned, it may be a server mod.
The Halloween event going on now has an effect that, when people exit the Underworld, they are Ubered, sped up, and do all crits for 10 seconds or so.
Obviously, there are also some new items that do more damage or increase speed:
The Soda Popper is a new Scattergun that does minicrits after a Scout has run around for a bit (to build a "Hype" meter).
The Winger is a new Scout Pistol that does 15% more damage, but only has 5 bullets per clip.
The Liberty Launcher is a Rocket Launcher that fires as fast as the Direct Hit but does the standard splash damage range, but it only has 3 rockets instead of 4.
The Disciplinary Action is a Soldier Melee item that make him and the teammate he hits with it move faster.
The Reserve Shooter is a Soldier/Pyro Shotgun that crits against players who are airborne and increases weapon switch speed.
The Splendid Screen is a new Demoman Shield that causes him to do damage if you get hit by the charge itself. Additionally, if he attacks immediately afterward with his melee weapon, the hit crits (like the Chargin' Targe does).
The Overdose is a Medic Syringe Gun that makes the Medic move 1% faster for every 10% he has on his Ubercharge, but does 10% less damage.
The Shahanshah is a new Sniper melee weapon that does 50% less damage if he has > 50% health, and 50% more damage if he has < 50% damage.
The Enforcer is a new Spy gun that does more damage than standard Revolver, but makes cloaking take half a second longer.