For maximum fun
from minimum expense
nothing beats the .22 Colibri
The .22 Colibri resembles the .22 lr but uses a pointier and lighter bullet that only weighs 20 grains and is propelled only by the explosion of the primer and has no additional gunpowder.
Frequently used as a shooting gallery round the .22 Colibri is powerful enough to knock down small and light steel or plastic targets.
It can safely be fired in any revolver, or pistol that is chambered for the .22 lr but due to its relatively low power will not cycle a semiautomatic action. Using it in a rifle is not recommended as the pressure it generates might not be enough for the round to clear the barrel.
For CQB with rats in the kitchen, the .22 Colibri would be just perfect as it would be powerful enough to wound those damn critters but not too powerful to damage our floors.