Surface and Materials
The upper part of the Pulsefire Core's shell is coated in matte UV-style paint that generally feels nice to the touch and provides enough grip for most people. The side buttons are glossy, the CPI buttons are textured matte plastic, and the scroll wheel has a rubberized outer layer. The whole middle panel with the scroll wheel and CPI buttons features a glossy finish.
As for the side panels, they are made out of a more grainy plastic and feature wave-like texturing and glossy inlays. Honestly, these sides feel a bit slippery with moist hands, I wish HyperX would have used the same material on the sides as they did on the top.
Build Quality
Build quality is ridiculously good on the Core. We're talking about a sub-$30 mouse, and I couldn't make it emit a single creak or squeak. Everything is aligned perfectly, and there is no rattling whatsoever, even the buttons have no play. Way to go, and I'm glad to see many manufacturers focus more on build quality lately.
Weight
The mouse weighs about 93 grams with a bit of cable (opposed to the 87 grams specified by the manufacturer), which is decent, and it is well-balanced, but as for me, I'd definitely go for something lighter. However, we're talking about a budget mouse, and casual users tend to like heavier mice more, so it might be more appealing to them. Generally speaking, a lighter mouse is better for your wrists in the long run.