Gouache, for those not familiar with the media, is basically a thicker and more opaque watercolour. Traditionally, it's been made with the same binder and with a much higher pigment load. These days gouache can also be made with an acrylic binder and the primary difference in behaviour is that it dries to a water resistant finish, similar to more traditional acrylic paints.
In either case, gouache is often used opaque or can be diluted to behave similar to watercolour. The end result, however, dries to a mat finish and, as a result, has been popular in illustration.
Holbein Designers Gouache - Yellow
Holbein Acryla Gouache - Crimson
Royal Talens Gouache - Light Blue
These three are professional grade, one of them acrylic based, the others more traditional. You can, in case you're wondering, mix acrylic and non-acrylic together. In addition, we also have:
Savoir Faire Gouache - White
Savoir Faire Gouache - Violet
These two are more of a student grade, but I didn't really notice a major difference.
Princeton Neptune Round #2 brush
Marabu Skyline Fineliner - set of 4 colours
Pretty good box this month. I have a metric ton of fineliners, so I largely ignored those, but the gouache a broke out to play with and created a surreal landscape (and not a very good one) just to test out some mixing capability. I did find that I hard time getting a black or gray, but I did get a brown. Anyways, because I like to show my bad art...