The Old Course at St. Andrews, famously, has a crossover at the 7th & 11th holes, although one rarely hears anyone mention that in discussions of the course.
I used to think it was a feature unusual enough that I would list any instances I saw in The Confidential Guide(s). Claremont in California has a couple of aggressive ones, and many of the Irish courses have at least one hole where you hit over the previous green. Royal Worlington & Newmarket has a few of those within the space of nine holes!
I'm told that Greg Norman wanted to have a crossover in his routing for the Moonah course at The National in Australia, but the club's lawyers wouldn't consider it.
I figured resistance to the idea would be pretty standard on modern projects, so I have not offered up crossovers as a solution on my own projects as often as I see the potential for them. But I've done it once or twice, notably at Tara Iti where the 4th hole turns inland from the shore and then the fifth tee shot plays 90 degrees across in front of the third tee to head back to a green near the beach. Again, hardly anyone ever comments on it, and I'm sure a fair percentage of people don't even notice since the course is not all that busy.
On my trip to India and Sri Lanka a few years ago, I saw crossovers everywhere, and I was amazed at how well the traffic worked itself out. Royal Colombo in Sri Lanka has a shared fairway for the 1st and 18th holes, which is no wider than a standard fairway, but I found it working great on a busy weekend afternoon . . . players on both tees would wait until the fairway cleared, and then both would drive into the same area, and say hello to each other on the way to their tee shots!
So, I've become a fan of crossovers, and you can expect to see more of them in my future work. There will be one or two of them at Punta Brava in Mexico, and at Cabot Highlands in Scotland. We had one in the plan for Sedge Valley, too, but wound up taking it out, because the walk to the "normal" tee made more sense once we moved the previous green site. We have fiddled with several plans that would have par-3 holes crossing in mid-air, where the foot traffic would then go behind the other tee to avoid danger [unless someone tops their tee shot].
Where have you all seen crossovers in your travels? What was the most ingenious, and/or the most dangerous? Do they bother you or fascinate you?