I'm getting to that point 34 hours in that all of my persona are starting out with more skills than the 8 they can learn, and I'm having to make choices that are going to affect how my game plays out.
So far, the most useless skill seems to be Trafuri, the one that lets you escape battle. Essentially it's just wasting a slot for an ability I'll almost never use because the only battles I'd run away from are boss battles where I'm getting destroyed, and you can't run from those. Also, you can get a Vanish Ball from the shop for a few bucks that accomplishes that exact same thing. Similarly, Traesto is also pretty useless because it can be used instead of a Goho-M to leave dungeons and those things practically grow on trees.
Alertness seems similarly useless, since I almost always go into a fight with player advantage by sneaking up on dudes. Sharp Student lowers chance of criticals on me, but I don't think I've seen a single one I didn't deserve getting hit by (e.g. not blocking constantly when an ice guy is attacking and I've got Yukiko on the field... which as an aside, is a little weird because the name means "Snow child" in Japanese and she's a fire chick.)
But then there are some of the attacks, like Hama and Mudo which both cause instant death with light/dark respectively, but at a very low percentage of probability. I'd pretty much never use them since I'd much rather have reliable damage. Similarly, Poisma/Poison Mist damage people too slowly, Fear attacks aren't reliable, etc. The only thing like that I've had some success with is Tentarafoo, which Yosuke gets automatically. It confuses/disables at least a few enemy characters at least during a battle and that's cool.
But like Enervation? Exhaustion? I have no idea how that affects gameplay.
Here's a list of all skills:
What else should I keep an eye out to get rid of? Anything that will unexpectedly become key that I should hold onto?
I've been putting Invigorate 1 on everyone new through fusions (Kinda wish I knew who had it originally so I can get some Invigorate 2 in there), as well as starting matches with persona with auto-something (usually attack-up / Tarukaja). I also lucked into getting a shuffle time that got me a random skill-up, and bumped one of my personas' Tarukaja to Matatarukaja, so it attack buffs the whole team way earlier than I should probably have that skill (I'm like 29 now). A good number of my guys end up inheriting that one.