Le Trône de Fer : le Jeu de Figurines - Arbalétriers Lannister

Crossbowmen are easier to train than their more archaic counterparts. 

However, the crossbow itself is more expensive to manufacture and maintain, especially on a battlefield. Even with minimal training, Crossbowmen can accurately pull and drill through heavy armor, even under direct load pressure. 

However, no decent General Lannister would dare to place his Crossbowmen near a melee!