Pike and shot
Origin: By the 16th century, late-medieval troop types that had proven most successful in the Hundred Years' War, Burgundian Wars and the late phase of the Reconquista, dominated European warfare, especially the heavily armoured gendarme (a professional version of the medieval knight), the Swiss, the Spanish Tercio and the Landsknecht mercenary pikemen. The emerging artillery corps of heavy cannons was a rapidly improving technology.
Emperor Maximilian I opposed the French armies in the War of the Burgundian Succession and the Italian wars and established the Landsknechte units. Many of their tactics were adapted from the Swiss mercenaries, but the use of firearms was added. The firearms, in conjunction with the pike formations, gave the Imperials a tactical edge over the French. Those pike and shot regiments were recruited in Germany, Austria, and Tyrol.
In 1495 at the Battle of Seminara, the hitherto successful Spanish army was trounced while opposing the French invasion of Naples by an army composed of armoured gendarme cavalry and Swiss mercenary infantry. The chastened Spanish undertook a thorough reorganization of their army and tactics under the great captain Gonzalo Fernández de Córdoba ("El Gran Capitán"). Realizing that he could not match the sheer offensive power of the French gendarmes and Swiss pikes, he took advantage of the shooting power of firearms, an emerging technology at the time, with the defensive strength of the pike, and to employ them in a mutually-supporting formation, preferably in a strong defensive position. At first, this mixed infantry formation was referred to as a colunella ("colonelcy"), and was commanded by a colonel. It interspersed formations of men in close order armed with the pike and looser formations armed with the firearm, initially the arquebus. They reappeared during the conquest of Granada with "El Gran Capitán". The arquebusiers could shoot down their foes, and could then run to the nearby pikemen for shelter if enemy cavalry or pikes drew near. This was especially necessary because the firearms of the early 16th century were inaccurate, took a very long time to load and only had a short range, meaning the shooters were often only able to get off a few shots before the enemy was upon them. 
This new tactic resulted in triumph for the Spanish and Fernández de Córdoba's colunellas at the Battle of Cerignola, one of the great victories of the Italian Wars, in which the heavily outnumbered Spanish pike-and-shot forces, in a strong defensive position, crushed the attacking gendarmes and Swiss mercenaries of the French army.

History: 

Ratios: The proportion of melee weapons to shot varied depending on the state and era, as did the exact weapons used. In general, the later the date, the more prominent firearms were. Due to this, the role of the pike changed over time. In the late 15th century and the first half of the 16th, the pike was an offensive weapon; by the end of the 16th and into the 17th, its niche was primarily defensive, though this did not preclude fights between pikemen. The push of pike became rare and battles were increasingly resolved by shooting. Directly linked to this was halberds becoming less common, as their primary role in breaking the push became less relevant and their secondary role (repulsing cavalry) was better filled by more pikes: the French regulars abandoned the halberd in 1568 (aside from NCOs), and the Dutch not long after, while the Spanish army, as well as those of various Holy Roman Empire states, would continue to use the halberd in limited numbers into the mid-17th century (the English used the similar billhook). The predominance of shooting was not a universal advancement, however. For example, in the Wars of Religion of the 1560s and 1570s, 54% of wounds suffered by French soldiers were inflicted by swords, these being the most common weapons on the battlefield as pikemen, halberdiers, arquebusiers, musketeers, and cavalry all carried them as sidearms.
In 1471, the Burgundian State organized its army into 1,250 lances of nine men each, thus its forces were 2/8 heavy cavalry (men-at-arms and sergeants), 3/8 mounted archers (who also carried hand weapons and could fight dismounted), 1/8 pikemen, 1/8 crossbowmen, and 1/8 handgunners; the last man in each lance was a noncombatant page.
The Black Army of Hungary was one of the first forces to use the arquebus to a large degree. In its 1477 to 1488 wars, 25 percent of its soldiers had firearms (both arquebuses and more primitive handgonnes), an unusually high ratio for the time. The average in Europe by the end of the 15th century was that 10 percent of the infantry were equipped with firearms.
According to a Castilian ordinance for "people of war" of 1497, Spanish foot soldiers were divided into three categories. One-third of the infantry carried pikes; one-third had swords and shields; and the final one-third consisted of crossbowmen and gunmen. It is in this configuration that the Spanish army won the first Italian Wars. In preparation for the Third Italian War of 1502 to 1504, Spanish general Gonzalo Fernández de Córdoba set his companies at 50% pikes, 33% swords and shields, and 17% arquebuses. This ratio was flexible and could be changed as tactics required. The Battle of Cerignola, which demonstrated the power of the arqebus, had the Spanish army roughly following this ratio, with the infantry being 25% arquebusiers.
Following its 1506 military reforms, Florence had an army armed 70% with pikes, 10% with muskets, and the remaining 20% with halberds, hog-spears, or other close-combat weapons.
In 1515 the Black Band's companies consisted of 70% pikes, 12% arquebuses, 12% two-handed swords, and 6% halberds. For landsknechts in general, the usual arrangement was that one Fähnlein, the standard unit, had 400 men, of whom 300 were pikemen (75%), 50 were arquebusiers (12.5%), and 50 were halberdiers or two-handed swordsmen (12.5%). Arquebusiers, halberdiers, and swordsmen all received double pay compared to pikemen.
The Spanish army standardized the tercio arrangement in 1534. At this time a tercio was 14 companies of two types. The first type, numbering twelve per tercio, had 219 pikemen and 20 musketeers. The second, comprising the remaining 2, had 224 arquebusiers and 15 musketeers. Thus, at full strength a tercio had 2,628 pikemen (77%), 448 arquebusiers (14%), and 300 musketeers (9%). However in practice, muster rolls showed that tercios averaged 1,500-strong and had a ratio of 31% shot to 69% pikes. The musketeers used a particularly heavy firearm which fired balls twice the size of an arquebus's.
In Venice the proportions were first fixed in 1548, at 10% halberds, 30% arquebuses, and 60% pikes. French contracts of 1562 simply specified 33% of arquebusiers. For the English 1571-2 campaign in France the recommended balance in newly formed companies was 6% halberds, 20% muskets, 34% arquebuses, and 40% pikes; this was adjusted in 1589 to 10% halberds, 30% pikes and 60% unspecified firearms. By 1600 France set a 1:1 ratio of pikes to firearms, and Spain 10% halberds, 30% pikes, 25% muskets, and 35% arquebuses. In 1560, following an order to increase the proportion of firearms, Spanish units in Italy became 54% pikes and 46% firearms. The Spanish average throughout the 16th century was 2 pikes for every 1 firearm.
In the 1570s the standard infantry company in Dutch service (whether they be Dutch or foreign hires such as Germans and English) had about 150 men, including 4 officers (a captain, lieutenant, quartermaster, and barber-surgeon), 5 NCOs (two sergeants and three corporals), 15 musketeers, 65 arquebusiers, 45 pikemen, 12 halberdiers and targeteers, and 3 musicians (two fifers and a drummer). A study of a selection of Dutch companies from 1587, standardized by William of Orange, showed 34% pikes, 9% halberds, 5% swords and bucklers, and 52% firearms.