The helmet Kabuto
The helmet (Kabuto) had many variations. Its general form was
Bowl (hachi) and the nape-guard (shikoro). Originally the hachiís where round but as time went by a greater range of helmet shapes where used. Some helmets are termed multi-plate because they are made from several plates to provide extra strength and beauty.
Face armour know as Men Yoroi would be face like and could include nose, cheek guard
The breastplate and back protection is called a Do. There are numerous variations on the design. The most unusual thing about he do was that it absorbed blows and still maintained mobility.
Other part of the armour are Gusari katabira (mail shirt), kote, (sleeves) sune-ate (shin guards) , kogake (foot guards) , wakibiki (armpit guards) and assorted armour
The main weakness for attack where
1) Throat, neck (under helmets protective guard)
2) Under the armpits and below the body plate at about groin height
3) Ankles between shin guards and foot.
4) If knocked to the ground inside of thighs and groin.
During the course of battle the armours security may well be degraded from repeated attacks creating more openings for attack.
Other weapons could also be used to penetrate the armour. Yari (spear see picture on next page) was particularly effective at attacking the above-mentioned weak points plus also able to pierce between any openings penetrated in the armour during the course of the battle. It allowed the attacker to engage the enemy while being outside of sword range. The attacker still had his Daisho(Katana and wakzashi) to fall back on when the Yari was lost broken or distance to close
Tanto (dagger carried in belt), and kozuka (see below) are a variety of small blades ranging from dagger down to small utility blade carried on saya (scabbard). They allowed the samurai to stab through all mentioned weak points plus eye and mouth holes in protective war masks built into many helmets and between many armour joints too small for a sword to find.
Helmet breaker designed to smash helmets or rip armour to allow exposure to sword technique (no picture available). In later years this evolved into the jitte a policing weapon.
This is far from a complete list of weapons that could be used on armour.