"weapon-fu" is term I use as a variation on kung-fu: meaning "knowing how and when to use a specific weapon...while also anticipating opponent's weapon choice"
Or you could just say "weap smarts"!
Sometimes I use the specific weapon name: "Pogo showed off some spectacular rox-fu in this(http://q2scene.net/ds/index.php?op=dd1&id=1169334982) demo"