Zardnaar
Legend
Back in the day weapons were not balanced as such but there tended to be a bit more variety in terms of what people would use. Maces, lswords, spears, daggers, darts etc would all get used for a variety of reasons along with more variety being used in terms of armor. This was partly due to things like speed factor which were used (smaller weapons were generally better for initiative vs spell casters), and the way initiative and magic items worked. Long story short initiative was rolled on a d10 or d6 so a 2 point difference in speed between a long sword and a short sword for example was like a +4 or +6 initiative modifier in WoTC D&D. Initiative was also rolled every round.
In modern D&D and derivatives there has also been a massive trend towards using the best weapon. In 5E this tend to be a great weapon, a pole arm, a longbow or crossbow, a rapier and a longsword depending on what class and feats you have access to. Armour has almost been reduced to studded leather and full plate. At least until you can afford something better. This trend also exists in Pathifnder with great swords, falchions, and longbows basically being the default weapons with the occasional scimitar being used. 3.x games basically have 3 types of armor- chain shirts, full plate, and breast plate and mithril and adamantine versions thereof.
In 5E this has gone as far as basically obsoleting simple weapons entirely. For example a monk will eventually deal more damage with his hands than the class weapons, spell caster cantrips deal more damage as well from level 5 onwards as a general rule. When was the last time you saw a PC use daggers as a primary weapon? If I had to hazard a guess there I would guess 4E or AD&D.
In TSR era D&D it generally did not matter if the PCs had 10, 15 20 or 100 +1 weapons as they could only use one of two of them at a time. In 3E and 4E those weapons could be sold and turned into a weapon the PCs actually wanted. 5E RAW you can’t do this as you may be able to sell a weapon but you can’t really buy one or create one as easily as you could in third and fourth edition and Pathfinder.
Now old school adventures are reasonably abundant in modern terms in terms of magic items. One could find a +3 or better weapon at reasonably low levels and a Paladin might have a +5 holy avenger from low levels. The difference compared to modern D&D is you would use that weapon for the rest of your career as there was no expectation you would upgrade it. 5E still kind of assumes this to some extent being roughly half way between OSR D&D and 3E/4E in terms of when you get magical equipment.
Official adventures and OGL adventure do have a reasonable amount of magic items in them such as HotDQ, RoT and the Quests of Doom book. I think magical items are the key to variety in 5E. Why would one wear chainmail when plate is the better armor? Well perhaps that chainmail is magical. A +2 or +3 great sword is erm great to have but it doesn’t really play well with the great weapon master feat. A +2 or +3 spear or dagger helps with accuracy but overall damage doesn’t sky rocket through the roof.
Some weapon styles also have better options available via feats and generally strength based feats are better for melee than dex based ones due to feats like Heavy Armor master, Polearm Master, Great Weapon Master and Shield Master. A dex based melee fighter for example doesn’t get the same level of feat support so the DM may help them out. A flametongue rapier or even a short sword would do wonders for them. Under normal circumstance a short sword is semi pointless except maybe for duel wielding.
Sword and board warrior types may be in a similar boat. At least the shield master feat is good but it is not always reliable if one is facing giants for example. Rather than putting in +2 armor consider a +2 shield instead. PCs can’t trade magic items in any more to get exactly what they want. A duel wielder is the weakest combat style in the game so a +2 or even +3 dagger and a +1 rapier won’t exactly break the game.
Now some of you may be considering this is unfair to the players who did pick an optimal style. But consider this what happens if you put in a flametongue great sword for say an avenger Paladin? His damage jumpes up to 4d6 damage per hit or 5d6 with hunters quarry and he gets to cleave and use the -5/+10 part of the great weapon fighter. By level 11 one could be looking at 5d6+15 damage or so per hit. Now Mr Sword and board did not get that flametongue weapon and he took the shield master feat. Not only is that feat situational but his damage by level 11 is going to be along the lines of 1d8+7 (str+ weapon style). 11.5 average damage vs 32.5 or 22.5 without the -/+10 part of the great weapon feat.
In this situation I would be inclined to make the flametongue sword a longsword or even a shortsword and at some point give the great weapon fighter a frostbrand or generic +1 item maybe with some sort of ability. This lets both PCs feel effective while not heavily rewarding one over the other and if the weapon is not 100% optimal (short sword vs longsword) they have a choice or sacrifice to make.
So if you as the DM get sick of seeing the same thing over and over again and want to put in some powerful magic items just avoid magical versions of the following weapons and armor or make them a bit more generic. If feats are allowed I do not recommend +2 or better great weapons and espicially hand crossbows.
Heavy weapons
Polearms
Longbows
Hand Crossbows
Rapiers
Longswords/1d8 one handed weapons.
Studded leather
Plate Armor
Splint Mail.
In modern D&D and derivatives there has also been a massive trend towards using the best weapon. In 5E this tend to be a great weapon, a pole arm, a longbow or crossbow, a rapier and a longsword depending on what class and feats you have access to. Armour has almost been reduced to studded leather and full plate. At least until you can afford something better. This trend also exists in Pathifnder with great swords, falchions, and longbows basically being the default weapons with the occasional scimitar being used. 3.x games basically have 3 types of armor- chain shirts, full plate, and breast plate and mithril and adamantine versions thereof.
In 5E this has gone as far as basically obsoleting simple weapons entirely. For example a monk will eventually deal more damage with his hands than the class weapons, spell caster cantrips deal more damage as well from level 5 onwards as a general rule. When was the last time you saw a PC use daggers as a primary weapon? If I had to hazard a guess there I would guess 4E or AD&D.
In TSR era D&D it generally did not matter if the PCs had 10, 15 20 or 100 +1 weapons as they could only use one of two of them at a time. In 3E and 4E those weapons could be sold and turned into a weapon the PCs actually wanted. 5E RAW you can’t do this as you may be able to sell a weapon but you can’t really buy one or create one as easily as you could in third and fourth edition and Pathfinder.
Now old school adventures are reasonably abundant in modern terms in terms of magic items. One could find a +3 or better weapon at reasonably low levels and a Paladin might have a +5 holy avenger from low levels. The difference compared to modern D&D is you would use that weapon for the rest of your career as there was no expectation you would upgrade it. 5E still kind of assumes this to some extent being roughly half way between OSR D&D and 3E/4E in terms of when you get magical equipment.
Official adventures and OGL adventure do have a reasonable amount of magic items in them such as HotDQ, RoT and the Quests of Doom book. I think magical items are the key to variety in 5E. Why would one wear chainmail when plate is the better armor? Well perhaps that chainmail is magical. A +2 or +3 great sword is erm great to have but it doesn’t really play well with the great weapon master feat. A +2 or +3 spear or dagger helps with accuracy but overall damage doesn’t sky rocket through the roof.
Some weapon styles also have better options available via feats and generally strength based feats are better for melee than dex based ones due to feats like Heavy Armor master, Polearm Master, Great Weapon Master and Shield Master. A dex based melee fighter for example doesn’t get the same level of feat support so the DM may help them out. A flametongue rapier or even a short sword would do wonders for them. Under normal circumstance a short sword is semi pointless except maybe for duel wielding.
Sword and board warrior types may be in a similar boat. At least the shield master feat is good but it is not always reliable if one is facing giants for example. Rather than putting in +2 armor consider a +2 shield instead. PCs can’t trade magic items in any more to get exactly what they want. A duel wielder is the weakest combat style in the game so a +2 or even +3 dagger and a +1 rapier won’t exactly break the game.
Now some of you may be considering this is unfair to the players who did pick an optimal style. But consider this what happens if you put in a flametongue great sword for say an avenger Paladin? His damage jumpes up to 4d6 damage per hit or 5d6 with hunters quarry and he gets to cleave and use the -5/+10 part of the great weapon fighter. By level 11 one could be looking at 5d6+15 damage or so per hit. Now Mr Sword and board did not get that flametongue weapon and he took the shield master feat. Not only is that feat situational but his damage by level 11 is going to be along the lines of 1d8+7 (str+ weapon style). 11.5 average damage vs 32.5 or 22.5 without the -/+10 part of the great weapon feat.
In this situation I would be inclined to make the flametongue sword a longsword or even a shortsword and at some point give the great weapon fighter a frostbrand or generic +1 item maybe with some sort of ability. This lets both PCs feel effective while not heavily rewarding one over the other and if the weapon is not 100% optimal (short sword vs longsword) they have a choice or sacrifice to make.
So if you as the DM get sick of seeing the same thing over and over again and want to put in some powerful magic items just avoid magical versions of the following weapons and armor or make them a bit more generic. If feats are allowed I do not recommend +2 or better great weapons and espicially hand crossbows.
Heavy weapons
Polearms
Longbows
Hand Crossbows
Rapiers
Longswords/1d8 one handed weapons.
Studded leather
Plate Armor
Splint Mail.
The only time we ever used speed factors was when I DMed and I made the players use it, anytime anyone else DMed they did not. Most of the time we didn't even modify spell casting with init mods, either. 
