What is the best air rifle pellet for short distance small game hunting?

Why is the pellet so good at killing game;at short distances? What did this type of pellet do to the small game upon impact?What is the best air rifle pellet for short distance small game hunting?
If you want to make certain it is ';lights out'; in one shot, look for a rifle that exceeds 20 ft lbs muzzle energy.


Such as this in .22 or .25 caliber


http://www.pyramydair.com/p/walther-falc鈥?/a>


http://www.pyramydair.com/p/walther-falc鈥?/a>


or these in .22...


http://www.pyramydair.com/p/benjamin-dis鈥?/a>


http://www.pyramydair.com/p/benjamin-she鈥?/a>


http://www.pyramydair.com/p/rws-34-air-r鈥?/a>


http://www.pyramydair.com/p/hammerli-raz鈥?/a>


http://www.pyramydair.com/p/mendoza-rm-2鈥?/a>


http://www.pyramydair.com/p/mendoza-rm-2鈥?/a>


Basically something that can fire a .22 14.3 grain pellet at least 800 fps or a .25 17.7 grain pellets at least 700 fps.


Some will say this is overkill, but the wound will be so devastating, even a mediocre shot will bring instant death.What is the best air rifle pellet for short distance small game hunting?
RWS Superdomes. Excellent pellet either .22 or .177