Position the prop wherever you want it (such as the pistol in the character's hand), and with the prop selected go to the object window, and choose Change Parent. Then deselect everything, and select the hand the prop is to be "stuck" to. Or you could go to the Properties section of the Parameters window and do the same steps under Set Parent.

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If you're joking that's just cruel, but if you're being sarcastic, that's even worse.