Tamiya Incorporated, or Tamiya, is a Japanese modelling company formed after World War 2. They are in many ways the model-making forefathers of most major companies printing plastic models in the land of the rising sun, going all the way from Wood to Metal to Plastic. They are considered the world's foremost scale-model producers of military model kits, and make paint, glue, and various other materials for said models. However most of Tamiya's scale-models are in 1:35 scale, so unless you're planning on sticking a bunch of extra guns on it and calling it a Baneblade, you're probably not going to be able to bring it to your next game, though there are some 1:48 models as well.
Painting and Modeling Equipment
While they do make paint, you're actually rarely going to find much of it in US/UK game stores nowadays: their paint is generally formulated with the impression you'll be airbrushing it on, and are not necessarily known for it's solubility in water thanks to alcohol being a key ingredient. It is good airbrushing paint, especially for your Local Guardsmen player due to all the military color-schemes utilized, but generally speaking is best utilized for their car and tank models, or your tank models, should you find any. Now usually found in specialty craft stores.
What you're far more likely to see on the other hand, is their modeling equipment. Tamiya makes plastic cement, Green Stuff, finishing abrasives, palettes, thinner, decal solvents, brushes, and bog-standard glue that is usually stashed somewhere in your FLGS. Definitely some useful stuff, especially when it doesn't have Citadel's name on it and the price is lower.
In case you needed a reminder that Tamiya was a Japanese company, there was a time in the late 80's where Tamiya produced it's own waifu mascot that had a Rabbit sidekick, where she would be riding around in an M1 Abrams or in one of their many, many reproductions of meatspace cars. She also got her own model kits, one of which involved her being in a bikini, in case you want a free ticket to a government watchlist. Sadly (or thankfully), she no longer graces any of Tamiya's boxes or instruction booklets, and anything with her face on it is now considered a collector's item.