For me (not ranked):
Vallejo Dark Sand,
Citadel Khorne Red,
Contrast Flesh Tearers Red,
Speed Paint 2.0 Metallic Enchanted Steel,
Speedpaint 2.0 Ghillie Dew
I really like Vallejo burnt red.
Vallejo black (super basic I know)
Vallejo German cammo dark green
Vallejo Metal Color gunmetal grey
Citidel Retributor armor.
These are just the ones I use a lot and enjoy using. I also really like ProAcryl for vivid base coats. Citidel paints are great for dry brushing. Don’t use contrast very often but recently discovered that I get really nice yellows by painting something skin tones and shading before finishing with one of citidel’s yellow contrast paints.
Citadel Mephiston Red
Pro Acryl Bold Pyrrole Red
Pro Acryl Bold Titanium White
Two Thin Coats Sir Coates Silver
Scale75 irati green