These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Demonic Spiders: Appropriately enough, the scorpions and the slightly-weaker scarabs. Able to inflict lethal amounts of damage at almost any range, capable of taking more damage than most heavy units, and surprisingly accurate, they fit this trope perfectly. Their only weakness is that they are vulnerable to status effects and cannot dodge as well as Light classes. Although you can recruit them, you will need to best them in the Insect Ze League: a 4 versus about TWENTY insect endurance battle. Arguably the hardest battle in the game.
When equipped with an Executioner's Sword, the Samnite's fart attack can instantly kill multiple enemies.
Langston the Minotaur, who can be recruited very early on if you choose Valens's campaign, can absolutely devastate any team in the game if you master the Swing Meter.
Valens can normally only obtain his father's equipment very late game. A clone of him appears in one cup and it can occasionally drop it.
Best example is the Hell's Fury skill, the reward for defeating a chain of sidequests. Huge range and huge damage.
The recruitable Undead Summoner Taithleach can if you equip him properly go from being a sub-par glass cannon to a nigh-invulnerable, one-hit killing AoE-machine with two extra lives. This might be the reason he's restricted from using in a staggering amount of the leagues in the game.
Romantic Plot Tumor: The relationship between Ursula and Valens never really goes anywhere except to make the ending sadder. Not like anyone expected a good romance in a LucasArts game.