The user possesses limitless physical energy, stamina, and vitality is essentially untiring and can keep working, fighting, mowing, etc. at optimal efficiency under any circumstances and for an unlimited duration.
Sakamaki Izayoi (Problem Children are Coming from Another World, Aren't They?)
Zombies (Quake Series)
Mummies (Quake: Dissolution of Eternity)
Ustanak (Resident Evil 6)
The Rowdyruff Boys (The Powerpuff Girls)
Alex Mercer (Prototype series)
James Heller (Prototype 2)
Minions of Set (Samurai Jack)
SCP-2317 - The Scarlet King (SCP Foundation)
Skeletons (Crypt of the NecroDancer)
Zombies (Crypt of the NecroDancer)
Sonic the Hedgehog (Sonic the Hedgehog)
Negi Springfield (UQ Holder)
Saint of Killers (Vertigo Comics)
Kanade Tachibana (Angle Beats!) is a prime example of this power, she can participate in any fight against opponents while producing almost no fatigue toxins in her body.
Due to her infinite energy generator, Android 18 (Dragon Ball Series) can fight indefinitely without ever tiring or wearing down,...
...allowing her to overpower and defeat Vegeta.
Majin Buu (Dragon Ball series) has limitless stamina which, combined with his powerful regeneration, allows him to keep fighting at his peak indefinitely.
As Magical Zombies, the Fork Maidens (New Blood Interactive's DUSK) are tireless, meaning they can fight within a battlefield without any semblance of fatigue, though can still get killed.
Because the Possessed Scarecrows (New Blood Interactive's DUSK) are inorganic in origin, it is impossible for them to get exhausted during intense battles until their opponents are defeated and/or killed.
As long as his vengeance isn't fulfilled, Kratos (God of War) can perform limitless physical activities, relentlessly fighting colossal opponents and entire armies without ever tiring.
Unlike the Powerpuff Girls, the Rowdyruff Boys' (The Powerpuff Girls) energy never wears down in battle. Instead, they continue fighting with no signs of needing rest.
Sakamaki Izayoi (Problem Children are Coming from Another World, Aren't They?) has exceptionally high power, because of this, as long as his opponent doesn't give up, he can continue to fight them with no signs of fatigue what so ever.
Due to their divine nature, The Minions of Set (Samurai Jack) possess a limitless amount of stamina and tireless bodies, allowing them to continue fighting and pursuing jack without the need for rest or sustenance.
Hercules (Marvel Comics) possesses virtually limitless stamina, allowing him to never get tired after any exertion.