Just my personal opinion.I dont claim to be an expert.
Most Advanced pistol:
Heckler-Koch Ultimate Combat Pistol - early prototype (2003
Most advanced sub machine gun:
HK UMP-45
Most avanced PDW:
HK MP-7 PDW (Germany)
MP-7 with extended stock and foregrip
Most advanced shotgun:
USAS-12 shotgun (USA / South Korea)
USAS-12 with 20 rounds drum magazine
Most advanced sniper rifle:
CheyTac Long Range Rifle System - Intervention sniper rifle (USA)
CheyTac Intervention .408 caliber M100 sniper rifle
Most advanced anti-material rifle:
Steyr AMR / IWS 2000 (Austria)
Steyr AMR 5075 prototype
Most advanced assault rifle:
F2000 with computerized fire control module/sight and 40mm GL
Most advanced machine gun:
General Dynamics 12.7mm / .50 XM312 Machinegun (USA)
Most advanced grenade launcher:
XM25 grenade launcher / air bursting assault weapon (USA)
XM25 grenade launcher prototype (possibly mock-up)