A pencil, quilt block, tiles for the floor, snowflakes, nuts and bolts, honeycomb, chicken wire and soccer ball!
There are no ordinary household objects shaped like a decagon. Some glasses or vases may be decagonal in shape.
There are few household objects that are shaped like nonagons. Some coins in a few countries are, but even these are rare designs.
As far as I know, a hexagon has 6 angles whether it is regular or not. Some may be obtuse angles, but they still count. So a hexagon where some of the sides go 'in' rather than 'out' is still a hexagon.
The roof of a house,
That's like asking "What makes a Chevy a Ford ?". A Hexagon has six sides. None of them have to be equal or parallel. A parallelogram has four sides. Two of them are equal and parallel, and the other two are also equal and parallel. To take a hexagon and make it a parallelogram, you have to do some serious cutting and welding.
A hexagon is a polygon that has six edges and six vertices. Some of the objects at home that are shaped like a hexagon are a Allen wrench, bolts, and a checker board.
Some objects that are shaped like an oval include eggs and footballs.
There are no ordinary household objects shaped like a decagon. Some glasses or vases may be decagonal in shape.
There are few household objects that are shaped like nonagons. Some coins in a few countries are, but even these are rare designs.
phone
A rubick's cube, an icecube, dice, baby block, some boxes, 2x2 Lego pieces
The Pentagon in Washington is obviously shaped like a pentagon. Black shapes on soccer balls, some road signs and the home plate on a baseball field are all pentagonal shaped objects.
A natural made rock
As far as I ah aware, they are not at all common. Drinks coasters are about the only things that I can think of.
some decorative household items, roofs on some houses, pyramids, pencil points, tent, and crayon points are in the shape of triangular prisms
A pyramid, possibly a roof, and tipi's. That's pretty much it......
A regular hexagon and some irregular ones will tessellate, But in general they will not.