Videos with lots of movement and color
Here's a link with some examples (YT Kids won't let you make playlists, unfortunately!)
Visual timers or sensory bottles--easy to DIY!
Lighting
Color-changing lights
Toys that light up
Christmas lights or other string lights
Drawing pads
Lava or glitter lamps
Artificial fish tanks
Bubble tubes
Fiber optic lights
Liquid sensory tiles
Nightlights
Projectors
Suction cups work for high chairs, wheelchair trays, desks, and tables. Lots of "highchair toys" are perfect for this reason.
Don't be afraid to use products meant for other age groups--this is not saying your autistic or high-sensory friend (or yourself!) is a baby, sometimes products are used outside their age ranges to meet people's needs.
Consider their independence level--safety is paramount. Do they throw things? Mouth them? I have put together sensory-friendly and safe recommendations for people with all sorts of needs. :)
I Spy
Sorting beads or shapes
Memory card games
Playing with light and shadow
Matching games and toys
Blackout curtains
Eye masks
"Sleep" headphones (headband headphones)
The Headache Hat
Sunglasses