I've built a handful of them.
High Pointe #10 was a natural, true punchbowl ... we just ran a drain up underneath it just in case. The problem with that is potential ice damage in the winter, but they never lost grass there as long as the course was open.
The left side of Old Macdonald #3 is also a natural punchbowl with a drain underneath ... however with all the water that comes off the hillside, I'm told there have been days where the maintenance crew will come over the hill and find a frozen pond on the left side of the green in the morning! They have to bust up the ice and sump pump the water before the golfers get there.
#9 at Ballyneal is a punchbowl, although I thought of #15 and #3 before it, when thinking of that course. The 18th at Old Mac and the 18th at Cape Kidnappers are personal favorites. Also, St. Andrews Beach #3 and #5, and Barnbougle #4 and #5. And we've got a couple we've shaped at our new project in N.Z., Tara-iti ... #3 is a great long par-4 with a low green near the beach, and #9 is a really narrow punchbowl up in the dunes by the clubhouse.