Or they just stop talking and look confused before slumping over dead. One scene I remember off the top of my head was in You Only Live Twice. James is talking to an Englishman who was his contact in Japan, (the same actor that later played Blofeld in Diamonds Are Forever), and as the contact was talking he abruptly stopped, got a pained look on his face, then quietly sank to the ground where Bond discovered the knife in his back.
I’ve never been stabbed, but I imagine my reaction would be more like “AAAAAAARRRRGGGHHHHH!!! Holy Shit I’ve been stabbed!!”