For me, it has to be that Matt Thornton aliveness clip off Functional JKD, which I think I first saw when Aesopian linked it on Bullshido in around 2004/2005. Immediately set off a lightbulb in my head, it has also been the basis of my teaching. Really good stuff. He certainly didn't come up with the idea, but Thornton did a great job of explaining and popularising the concept. Lots of other clips I could mention, but I'll wait for some more people to post. ;)

https://www.youtube.com/w[...]mjmLWj5WCU

In addition to the above mentioned Matt Thornton chess clip I have 2 really important inspirational ones: Genki Sudos Westside nogi highlight and old Sherdog Carlos Newton MMA highlight. These made me think that grappling per se and grappling in MMA can be so super cool that I really want to do it not just to test myself but also because it's SO DAMN AWESOME!

https://www.youtube.com/w[...]IUWH-tuGGk

and

https://www.youtube.com/w[...]B0YnAf2XkU

And as a bit of a different kind of mention... The "Furious Angels" highlight I probably saw in 2008 first. It brought tears to my eyes when I first saw it (was studying in Unviersity Library and stumbled upon it) and still gives me goosebumps to this day.
https://www.dailymotion.c[...]deo/x2hym4
At that time I already considered myself a fighter... I had my seasons of hard training, my first fights. I had followed all these guys' fights and careers that are used in the clip. I thought I knew how it all felt... and wanted to go on.

(Background music played also a huge part in all those.)

And as Jorgen has posted, I'll mention another super important clip (well, its 1.5hrs, so maybe 'clip' isn't the right word) for me: the functional half guard vid he did years ago with Indrek. That formed the basis of my half guard. I still find it amazing that two guys in Estonia, who at the time were white and blue belts (I think? Jorgen can correct me), produced an instructional that was better quality and more useful than 90% of what I'd watched from black belts. It was therefore quite bizarre to actually meet Jorgen at a BJJ Globetrotter Camp a few years ago: he never quite seemed real, all the way from exotic Estonia. :P

https://www.youtube.com/w[...]fFzALZPhQc

Which I just realised means that Estonia has probably influenced my game more than Brazil, given how Jorgen and Indrek built my early half guard, while Priit has helped me not die in open guard so much (though I guess I already did the running escape after watching Saulo teach it on Jiu Jitsu Revolution 2, but Priit and Chris P has added so much detail :D).

The aliveness clip of Thornton shaped my view on Martial arts training. I saw it before i started training.

While I feel Royler and David Adiv mostly influenced my bjj as a whole, JJ Machado's approach as seen on his comp footage and instructionals I got back when I was a blue belt had really shaped most of what I still do from the bottom.

Starting out I admired (still do) Demian Maia's jiu-jitsu game because it seemed attainable since he didn't rely too much on natural abilities (i.e. freakish athleticism, insane flexibility).

His Head Control concept for defending guard passing is something I still try to remember/utilize. Especially for guys who like to pressure pass.
https://youtu.be/sRgoNsqKunI?t=171

I practice Judo and Sambo as well, but Jimmy Pedro's Grip Like a World Champion changed my stand up game completely, and it works wonders in Jiujitsu as well, what I've found is that if I can out grip someone standing it makes succcessful takedown much easier and if your opponent has a bad grip and tries to pull or jump gaurd, its much much easier to pass.

I'd say it was the little 5 sec. clips of Royce Gracie pulling off chokes and armbars between fights during the first few UFCs. They were pretty standard, but in 1993-1995, it was like seeing a Jedi in real life. I had done Judo for many years, but seeing those little 5 sec. "I'm Royce Gracie" clips of him submitting his brothers just blew my freaking mind.

A close second place was seeing Marco Ruas fight for the first time. I saw him in the back of Black Belt magazine in the early 90';s and I thought he looked ridiculous. He couldn't possibly be as bad ass as the 9th and 10th degree Kempo guys like Larry Tatum, or the Kung Fu masters, but........then I saw that guy fight. he was like a panther, huge hands and feet, carved from stone, just wrecking guys with his strikes, then he pulls off a leglock and I just had no idea how badass that guy was.

Like for Johannes, Can and Jorgen, the „aliveness“ Clip by Coach Matt Thornton was the toss for me in the right direction, too.
Coming from Law Enforcement, BJJ was for me not only fun on the mat, but another „tool in my belt on duty“/ delivery system(my friend and coach Roy Marsh always says: Jiu Jitsu is the art of control and not the art of Submission).
So what had a huge impact on me and my approach and development was ISR Matrix (Luis Gutierrez, back then Paul Sharp, Fletch Fuller), which was/is a concept using bjj as One of the delivery systems. Here the old teaser from like end of the 90‘s. or so. They put out a 5 DVD’s set back then (LE stuff too).
https://youtu.be/j9C8pBtwKbk

Stay safe out there, best regards, Mirco