This was an idea I got from our Parents as Teachers educator and modified to use what we had around the house.
I took a Gatorade bottle (we down this stuff at our house) and removed the label, then thoroughly cleaned it inside and outside. I filled it with some colorful pompoms, a couple strings of beads and a bag of metallic confetti. I picked these things because they were a) colorful, b) would make noise (the beads), c) had a variety of sizes, and d) were on sale at Hobby Lobby! Anything bright, colorful and interesting to look at would work.
I ran a line of hot glue around the top and screwed the cap on, then used an incredible amount of electric tape (because it's what I had around) to secure it and cover the lid.
When Ellie was a newborn, I'd hold this above her head during diaper changes and put it on the floor to encourage tummy time. When she started sitting on her own, she loved holding this, examining it and shaking it. It was also useful as a roller toy to encourage her to crawl. She finally started to get bored with it around 10 months, so I'm going to make her another one filled with rice and small objects to play I Spy.