Generally it's a combination of the rim/tire that can make a tire difficult to mount. Some people have no trouble whatsoever mounting up a Marathon +, others write us notes telling us how cruel we are to make such a tire. Mounting lube (soapy water), and talcum powder are usually worth employing, especially on these tires. Another trick that can work when all else fails is using zip ties to collapse the tire on one side (after mounting that side) to provide some slack on the unmounted portion of the tire. Here is an extreme application of this technique:

Specialized Armadillo. Crappy ride, also. Only tires in good condition I've ever thrown out.

Used this and 2 Park TL5s to mount my Schwalbe Marathon Plus'. 28mm onto Alex R500s. Really tough. Had to use liquid soap, too. The height of a given rim is also important. 25mm SMPs onto Sun CR-18s was relatively easy. But, on my high flange fg wheelset they were a *****.

That being said when I have had the rare flat or slow leak they do come off and go back on much easier than they mount. All of my bikes are equipped w/3 Pyramid 'flat spoon' tire levers w/t edges and burrs filed off. The only place online I know of to get them is https://www.bikepartsusa.com One's lbs probably has them as well. They're only around 4-5.00USD per set.

Vittoria Diamente pro, only because each time I did, I already knew I was about to get another flat soon.

Another vote (& Broken tire iron) for Vittoria Randonneur. The VR has been a good front tire for me but I wear them out quickly on the rear. I'm currently running a Michelin city on the rear (which was no picnic to put on either, btw).

I have had epic wrestling matches with 26x2.35 Big Apples.

I was taught over 30 years ago to never use a tire iron for installing, they are only used for removal. I've used similiar techniques to the the video above and always managed perhaps with some swearing and sweat. I'm not saying I won't ever find one that I can't get on, but I've changed a lot of tires on a lot of different rims. I quess I've been lucky.

I've used water from my water bottle to lubricate the bead. Even water is better than a dry bead against a dry rim.

****UPDATE*****
After pinching the tube installing my marathon plus, I left the tire on the bike for a few days and then decided yesterday to give it another shot with a new tube.

While it was a little difficult, I think that after the initial disaster, swapping the tire subsequent times is much much easier.

Schwalbe Marathon+. Sort of like Superman's Kryptonite.

I can't sat I've had issues with specific tires. Most take 5 to 15 minutes to remove and re-install. A little longer when they are new. But I did have a hell of a time installing tires on my previous rear rim on my mtb/winter bike (26" Axel - don't remember the exact model) . I've broken a few tire leavers trying to get tires on that one. Even the LBS couldn't get the studded tire on last winter. The front one with a unlabelled stock rim was a piece of cake to install a tire. It was the same LBS that had installed that rear rim a couple years earlier so they replaced it for next to nothing just to get the tire on.

far and away the most difficult tire i've ever had experience installing on a rim is the schwalbe marathon plus.

i've had two sets of marathon pluses in my life, a 20" set for a dahon folder, and a 26" set for an old MTB commuter conversion. in both cases getting the tires on to the rim for the first time took an unbelievable amount of effort.

the best thing about installing a marathon plus is that after you've done, all other tires will seem ridiculously easy to install.

Another reason I avoid Schwalbe tires, besides the cost. Very happy with Maxxis Overdrives. Easy on/off. Not quite as durable as Marathons probably, but for $30, no problem.

I've learned to buy tubes one size smaller than suggested by the tire width. Makes for easier installation, less chance of pinching.

I take it 1 inch at a time and in between lever lifts I feel around with the extra lever to make sure the tube is still tucked inside the tire, then another inch, ect. Especially with road tires since the leverage to insertion depth ratio is the smallest, then yeah, you will have a greater chance of pinching if you stick the lever in as far as you do a MTB tire. So to solve that you have to not stick the lever in so far. It makes it harder to leverage the bead on without the level popping out, but it saves $$$ and works for me.

I can just hear it now, the guys at schwalbe laughing at all of use in this thread.