Get the Huckleberry ice cream near McDonald. It's a little further away, but if you can make it up to Waterton in Canada, that is amazing. Crypt Lake in Waterton might be my top hike anywhere.
1. Highline Trail - Longer and more difficult, but less crowded and great views.
2. Iceberg Lake - More crowded but shorter and better for kids. Great lake hike with some awesome waterfalls along the way.
3. Swiftcurrent Lake - Less crowded part of the park, good for camping and some hikes. The water was colder.