These are actually different questions. 1. Reliable: consideration must be given to the AK-47 for reliability under all conditions, with secondary consideration to the type 45 and 57 SKS. 2. accurate: If you're talking about small arms, then the M107 semi-automatic .50 BMG sniper rifle. At 1000 yards, it's accuracy is limited only by the skill of the shooter. In auto: HK416. 3. Durable: measured by ability to operate under extreme exposure, it's the AK-47 or variants thereof (eg AK-74, with 5.45x39 round). Second place: any Mauser bolt-action. As an all-around assault rifle, the AK is the winner, bang-for-buck. If price is no object, you can look at the SA80 (Small Arms for 1980s) family from Enfield. It is the designation for a revolutionary family of assault weapons. On its introduction, the L85 Individual Weapon (IW) proved so accurate that the Army marksmanship tests had to be redesigned. The British Army uses the L85 Individual Weapon that replaced the rifle and sub-machine gun, and the L86 Light Support Weapon (LSW) that produces higher volumes of fire and is effective at longer ranges. Pretty good all-around design and reliable to boot.