I usually watch an OP once for a show and then skip it each time afterwards. That being said, there are a handful that I remember making the choice to always watch each episode. In no particular order:

• (NSFW) B Chiku Sentai SOX - “SHIMONETA: A Boring World Where the Concept of Dirty Jokes Doesn’t Exist” - I always laughed at the visuals of this more than anything. This show was wild.
• Onegai Muscle - “How Heavy Are The Dumbbells You Lift?”
• Idol - “Oshi no Ko”
• Zeitaku na Saji - “Campfire Cooking in Another World with my Absurd Skill”
• GO!!! - “Naruto”