We are so used to computer-generated special effects in movies that we sometimes forget how difficult and ingenious old-school practical effects were. Terminator 2: Judgment Day came out 30 years ago. Recall when gunshots were fired at the T-1000 terminator, which was made of an intelligent liquid metal. Bullets wouldn't stop him, they just made a metallic "splash" on his surface. That wasn't CGI at all! Instead, those were foam rubber and metal splashes that burst from the actor's clothing, created by master effects artist Stan Winston. You can see that they worked well in the test footage here, shared by the Stan Winston School of Character Arts.
Learn how Winston and his team designed and built this effect at Hackaday. -via Damn Interesting
Bonus: Here is test footage of the later effect in which the T-1000's head gets blown in half.
He recovered rather well from that one, too.