I have two favorite blanket patterns. One is a Twin Rib stitch. It looks like ribbing but lies flat and doesn't stretch. This is reversible and looks the same on both sides. Cast on in a multiple of 3. The first (right side) row is knit 3, purl 3 across. The second (wrong) side row is k1, p1 across. Repeat for pattern. This is a good stitch to use if you're making a scarf as a gift for a guy. It doesn't matter if the wind blows it up because it looks the same on both sides.
The second one is a thermal stitch. This does make a very heavy (weightwise) blanket. It looks like the waffle weave on long underwear and is very warm. This is cast on in multiples of four. The first row is knit across. The second row is purl across. Rows 3 and 4 are knit 2, purl 2 across. Repeat these four rows for pattern. When I knit this one for my DGD I used Bernat Baby Sport weight yarn and it was still quite heavy. This has become her favorite blanket.