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.
Designated Hero: Jason, full stop. His goal to take back his kingdom may be admirable (though we don't know for sure if his father Aristo wasn't, say, a brutal tyrant), but it's hard not to notice his blatant indifference to the loss of crewmen over the course of his journey or his plans to filch the Golden Fleece out of Colchis.
Averted in the Hallmark film where he must find the Fleece or else his mother will be killed.
Hilarious in Hindsight: Brian Thompson plays Demigod Hercules in the Hallmark film. A few years later he would get bumped up and play Cronus in Charmed.
Ho Yay: Hylas and Hercules sure do pair up quick. Hylas essentially dies trying to pick up after his thoughtless boyfriend and, afterwards, Hercules quits the quest to retrieve his body.
Narm: A good chunk of the Harryhausen film due to Todd Armstrong's awful acting, the fight with Acastus in particular. The harpy scene also fails to be anyway intimidating.
The last few scenes in the Hallmark one are made comical by the fact that Pelias is actually wearing the Fleece and looks quite ridiculous.
The fight with the Skeletons starts out ok, as they silently, slowly march forward...before letting out a high-pitched "war cry" that sounds like a pack of angry schoolgirls. The scene continues on and is rightfully lauded, but for that one moment...
Nightmare Fuel: Everything with Talos in the Harryhausen film, from the moment he wakes up and starts chasing the Argonauts to his death scene, where he grabs his throat and starts making noises like screeching metal.
One-Scene Wonder: Honor Blackman steals the show in the Harryhausen film, playing Hera. Olivia Williams steals the show in the Hallmark film, coincidentally also playing Hera.
Visual Effects of Awesome: Every monster in the movie, but the crowning moment is undoubtedly the fighting skeletons scene. That 3 minute scene took Ray Harryhausen 4 months of solid work!