Smokescreen Math
Starting in approx. 2015, the world watched while the various lords of the Internet flushed writers out of their walled digital gardens and replaced them with video creators. The great "pivot-to-video", first initiated by Facebook's demented advertising algorithms, eventually ended in the universal belief (in the minds of bosses and executives everywhere) that no one wants to read anymore and we should only be making videos.
This pivot, combined with Youtube actually having one of the higher-tier payment structures, together resulted in hour-long videos like the one below.
Mathhammer is the best kind of hammer analysis
This guy used math to run through which 40k stratagems were ACTUALLY good. This is the kind of analysis I want. But I don't want to watch for an hour to get this information. And just look at that thumbnail image. Truly I am an old, yelling at clouds.
The number one stratagem is of course Rapid Ingress. It allows you to bring a deep striking unit down at the end of your OPPONENT's movement phase. It's easy to see why that's good.
But I was shocked to see Smokescreen at number 8.
Smoke Launchers have been around long enough that my 30-year-old Rogue Trader-era Predator Destructor tank had them modeled on its turret. When its turret broke, around about the year 2000, I glued a straw where the barrel was supposed to go, spray painted it black, and continued my business. I fired the gun a lot. But for another 25 years or so, I never tried to use those smoke launchers.
A couple months ago, I found a 2nd edition-era turret for sale on eBay and finally replaced the old one. And now it doesn't have smoke launchers, and I am discovering I sort of want them now.

Smokescreen doesn't automatically save your tank or anything, which is why I probably originally discounted it. It only does two things.
1) Turns a 3+ roll to hit for most space marines into a 4+ to hit.
2) Adds an extra pip of armor save (due to Cover) which means you save on a 6+ against a successful lascannon hit vs. no save at all.
Neither of these bonuses "feels" spectacular. But taken together they apparently add up. I'm not good at math myself, so having someone else do it makes all the difference.
Another big thing I didn't really think about hard enough: You don't use Smokescreen until your opponent has confirmed that they're shooting at your tank. And then it applies to all other shooting that tank receives for the rest of the phase.
You will guarantee one unit's anti-vehicle attacks are affected, and you will make them think twice about using any more attacks on that tank.
Smokescreen is Warphammer Math's #8 core stratagem out of 12. But before watching this video I personally probably ranked it #12.
After watching the video I'm going to start using it like its #3 at least.
Again, not very good at math.