Enrichment!! One of my favorite topics.
I'm a behavior specialist at a shelter, so I try to get creative with enrichment as much as possible. We love to do snuffle parks and shreddable snuffle boxes as well as snuffle mats.
We also love to do "confidence courses" which include all kinds of novel items for the dogs to explore, like tunnels, skateboards, baskets of laundry, gates laid out on the floor (we love throwing treats in the crevices to encourage them to climb across the surface and investigate!), etc..
For our diggers, I like to fill a baby pool with towels (some have scent, some don't), so they can dig and bury their bones and whatnot.
Cats! We love puzzle treat toys (you can feed them in an egg carton so they have to work for it a bit, or bat the food out...same with boxes that have different sized toilet paper tubes...great for treat puzzles!), and different textured surfaces (bathmats and rugs, pillows, sometimes crunchy paper or bubble wrap). We do clicker training with some of the cats too. Bubbles are great for the active ones, and many of our volunteers like to sit and read with the more reserved ones. We also make toy mobiles when we have time, with jingle balls and stringy things dangling off of them.