I wanted to create a cube where Vampire Nighthawk can really shine (but that feels actually built around cards like Nighthawk). The cube is combat-focused, with most of the cards having short, simple text boxes.

Each color pair has 5 sign-post cards, each of which is a permanent and which mentions or contains a mechanic (with the exception of Karlov, who's cool, and all of Simic, which didn't really have a good keyword to use).
WU: Flying
UB: Flash
BR: Menace
RG: Trample
GW: Vigilance
RW: Haste
WB: Lifelink
BG: Deathtouch
GU: Lands
UR: Prowess