We were on the August 4th sailing and the only rainy day we had was in Ketchikan. They were giving out ponchos to people on excursions, but not for everyone leaving the ship. My DH and son went fishing, not booked through Disney, and they did not get ponchos. My dad and I did the duck boat tour, through Disney, and we did get ponchos. My mom and daughter were supposed to kayak, but it was canceled due to weather. They went shopping instead and did not get ponchos when they left the ship.
It was a nice gesture, but the ponchos were really cheaply made. Mine ripped right down the middle when I tried to take it off.
On board, one unique item that we saw was a Disney Alaska Tervis tumbler. I did not see it in the gift shops at all, but on the Tracy Arm day a little stand was opened up on deck 9 and that's where I saw it. There were only 4. The CM said those were the only ones available on the ship. They went really fast.
If you're looking for unique items in port, you will have to walk a little farther to get past the big tourist shops and the numerous jewelers. There are a couple in Juneau that I liked but I can't remember their names. Same with Ketchikan. I didn't shop in Skagway.
In case of rain, I recommend bringing a ziplock baggie big enough to hold your personal items that you can stick in your pocket to go shopping or to an excursion. In Ketchikan the rain was a steady rain and we really got wet, even in rain gear.