Let's look at the stats for a typical sword and spear from Tunnels and Trolls 5th edition:
Spear (6') 3+1 ST 8 DX 8 Cost 22 gp Weight 50 Range 40 yds
Saber (3') 3+4 ST 9 DX 10 Cost 55 gp Weight 60
From a strict sense of damage potential, the sword is better choice if you have the money, strength, and dexterity. The saber generates between 7-22 hits (average 13) while the spear on generates between 4-19 hits (average 10).
But weapons can be more than a list of numbers in a game. In reality, spears are the perfect all-around weapon. They are excellent at keeping enemies at bay when paired with a nice shield, especially when you have three of four other spear-wielding friends by your side. That 6' shaft allows you to hit your enemy first, especially if that enemy is wielding a 3' sword. This is also useful if you happen to be facing mounted opponents. Due to it's length, the spear can be wielding with one or two hands; when used two-handed the spear should be able to deal more damage as more force can be applied to the point of the blade. While typically used as a thrusting weapon, the spear can also be used as a slashing weapon if the spear head has a broad blade or the shaft could be used as a bludgeoning weapon. Of course the spear can also be thrown when needed, killing your opponents before they even get close enough to attack you. Try that with a sword. Once the battle is over, a spear makes a handy walking stick and they are good for probing the ground in front of you that may not be as stable as it looks (or checking the depth of a pool of water, pushing and nudging objects from a comfortable distance, pushing open doors, or even enchanting into a makeshift staff). Why carry around a 10' pole that you have to cast aside when trouble starts when you can carry a spear?
Unfortunately while all of this can be taken into account during a group game without need of special rules, the same is not true of solo adventures. In group games controlled by a GM, players have much more freedom of action. If the party wanted to form a wall of shields and spears to hold back a horde of monsters, for example, the success or failure of this action is dictated by the GM who can adapt and improvise as he/she sees fit. If nothing else there is always a saving roll that can be called upon. Solo gaming, however, always presents a problem when trying to be clever with your equipment. As a player, you can act as your own GM, making judgment calls and saving rolls as you see fit. This is especially true of non-combat uses of spears and other pole-weapons such as probing for pits and traps. But I was considering some house rules for using the common spear in combat to make them a bit more popular. I'll be trying these house rules in some solo adventures to see how they work out.
Spear House Rules
Two-handed wielding: When wielded 2-handed, the common spear is a 3+3 weapon.
Bludgeoning: The spear may be wielded as a staff (bludgeon) for 2 dice (useful if your opponent takes less damage from thrusting weapons).
First strike: When attacked by opponents with weapons 3' long or less, the spear wielder may make a L2-SR on DEX to get one free attack before the opponent closes.
I have gotten to the point where I equip all of my warrior characters with a spear and shield to start with along with one or two other hand weapons, typically a short sword of some sort and a dagger that can be wielded together for close and dirty fighting. A sling is usually a good thing to have a well just in case. At 1 gp why not have one? I've found this combination of weapons provides a nice basic tool kit to work with in nearly any situation.