Apart from some relatively minor use of combination weapons such as gun-swords and gun-axes, it should be noted that a combination weapon was the dominant infantry weapon for much of the last 300 years: the rifle with bayonet.

Whether a weapon sees significant military use depends on many things:

• Is it cheap enough?

• Is it reliable enough?

• Is it effective enough?

• Is it compatible with the other weapons being used?

Many combination weapons fail on the first three of these points. In particular, to avoid making a gun-sword or gun-axe too heavy, the gun must be light, and therefore small - the pistol-sword is generally a better sword than a musket-sword. This tends to make combination weapons like these more popular as cavalry weapons rather than infantry weapons. The other effectiveness issue is that the non-gun part of the weapon can make reloading more difficult, and therefore slower. Considering that a cavalryman can easily enough wear a sword at his side, and a pair of pistols in holsters on the horse, and perhaps an axe or mace as well hung from the saddle, it can be better to have separate pistols and swords.

The bayonet suffers from these problems, too. Since a pistol would be ineffective as a main infantry weapon, the gun is a full-sized musket or rifle. This makes the combination weapon - the gun with fixed bayonet - inferior to a spear as a hand-to-hand weapon. Why then is the bayonet so popular? Unlike the cavalryman, the infantryman cannot be reasonably expect to carry both pike and musket. But the question isn't whether 1000 pikemen would beat 1000 bayoneteers in hand-to-hand combat. A better question is whether 1000 pikemen would beat 1000 musketeers equipped with bayonets, when both are part of a balanced armies. That is, is it better to have 7,000 musketeers and 3,000 pikemen (plus cavalry and artillery), or 10,000 musketeers with bayonets (plus cavalry and artillery). When the battle is largely decided by fire at a distance, 'tis better to have more musketeers. Note that the pike is multi-functional - it can be used by infantry to fight other infantry (and could be very effective for this in Swiss and Landsknecht hands), and can also be used to protect musketeers from enemy cavalry. As the role of the pike in battle changed from a major offensive weapon for the infantry battle to the more auxiliary role of protecting musketeers, the bayonet vs pike equation changed. Whether or not a musketeer with bayonet could beat a pikeman in hand-to-hand combat mattered less, and the question became whether or not a musketeer with bayonet could hold off enemy cavalry without the assistance of pikemen. Thus, the bayonet replaced the pike on the battlefield.

Although horsed cavalry has disappeared from the modern battlefield, and role of the bayonet has ceased to be one of holding off enemy cavalry, the bayonet continues to soldier on. It lacks competition from enemy spears, so bayonet vs spear is a non-issue. Whether the bayonet is effective enough in battle depends on the effectiveness of rifle with fixed bayonet vs rifle without bayonet, and bayonet vs short weapons such as knives, hand-held bayonets, clubs, etc. Against both, the bayonet has the advantage of reach, and against the rifle alone, the benefit of a sharp point (but note that rifles without bayonets (or ammunition) are used as weapons in hand-to-hand combat, as clubs, even in modern warfare). It's also worth noting that much of the use of the bayonet in modern warfare is psychological - the enemy often flees or surrenders in the face of an obviously determined bayonet charge.