In films such as Jason and the Argonauts and the various Sinbad movies, model animator Ray Harryhousen created some spectacular special effects.  One of those effects was that of skeletal warriors wielding swords and carrying shields.  Ray Harryhausen's skeletons are fast and nimble, appearing to be more formidable opponents than the skeletons in the D&D Monster Manual.  This has inspired a variant monster: the skleros.  Skleros is Greek for dry and hard and is a root for the word "skeleton."

Skleros (skeleton variant)
Medium Undead
Hit Dice: 1d12 (7 hp)
Initiative: +7 (+3 Dex, +4 improved Initiative)
Speed: 30 ft
AC: 16 (+3 Dex, +1 shield, +2 natural)
Attacks: longsword +4 melee
Damage: longsword 1d8
Face/Reach: 5 ft x 5ft/ 5 ft
Special Attacks: Instinctive tactics
Special Qualities: Undead, Immunities
Saves: Fort +0, Ref +1, Will +2
Abilities: Str 10, Dex 16, Con - Int -, Wis 15, Cha 8
Feats: Improved Initiative
Climate/Terrain: Any land and underground
Organization: Solitary, Any
Challenge Rating: 1 
Treasure: None
Alignment: Neutral
Advancement: --

Skleros are skeletons made from the corpses of highly trained warriors (characters with at least a +4 attack bonus) that still magically retain some of their past fighting skills.
 
Combat
     Instinctive Tactics (Ex):  Skleros remember many of their former fighting habits.  Despite not having intelligence, skleros can still somehow use tactics when fighting, such as using formations, flanking maneuvers, et al.
     Undead:  Immune to mind-influencing effects, poison, sleep, paralysis, stunning, and disease.  Not subject to critical hits, subdual damage, ability damage, energy drain, or death from massive damage.
     Immunities: Bloody bones have cold immunity.  Because they lack flesh or internal organs, they only take half damage from slashing or piercing weapons.

Monster converted from first edition version presented in the October 1988 issue of Dragon Magazine in the article "The Ungrateful Dead" by Tom Moldvay.