I never really use Cyclone trap. However, believe it or not, I use Insect Swarm quite a lot. It was very useful on the last boss.
No, I didn't.
I'd have to say the Plasmids that usually ended up being stored in the Gene Bank, never to be used again were Security Command, Hypnotise BD, Enrage and Target Dummy. The one I used least was Target Dummy, I really didn't see the point.
Scout; not wasting my ADAM on that
I feel like plasmids were underpowered in general late-game compared to special weaponry and the crossbow. Weapons become massively strong (reusable inferno bolts, easy trap bolts and easy antipersonnal pistol ammo come end game) throughout the game while plasmids become increasingly weak.
That's not to say some don't remain extremely useful, it's more that the plasmids you buy later in the game are much less useful then the ones just handed to you at the beginning, where the opposite is true of the weapons.
Electrobolt and Telekinesis are massively useful. Incinerate is good for crowd control and explosions. Winter Blast (which I never take past rank 1 due to eve use) is good for buying a second or so against a Big Daddy (mess up Bouncer charges for example), trapping a houdini long enough to line up a bolt or freezing a bot/turret for an instant hack (much better than electrobolt (10x that for eb3) eve-wise).
The problem I have with half of the remainders is that they're just too slow and they come too late. Hypno BD is heavy on eve, puts you at risk once your control ends, and is rather ineffective. Waiting for something to hit you sucks. Cyclone is trap based, but so many better traps can be made if you're willing to invest the time (trap bolts, prox mines, gas canisters, oil slicks, hell even some water and electrobolt). Security Bullseye is massively cheap and awesome (especially since it doesn't aggro) but requires a lot of set up unless fighting the last boss, and requires a very passive player.
The other half are much quicker to use... but fairly underpowered and come later as well. Enrage is humourous and I will admit, even useful at times, but generally I rather headshot 4 splicers than throw enrage on them all and wait (I wouldn't do both, that's just a waste of resources after all). Target Dummy seems a bit buggy as it usually doesn't work for me... if it worked more often it'd definitely be worth it. And I kind of hate IS for it's animation/effectiveness.
So basically I have three tiers. Love: Electrobolt/Telekinesis | Like: Incinerate/Winter Blast | Eh: The Rest.
So a 6 way tie of least favourite (thus the massive post).
If I'm arsed to buy more than 4 slots the lineup is: Main four, Security Bullseye, Target Dummy. I consider Insect Swarm pretty equivalent to Insect Swarm so it's an either or. We could say the remaining three are my least favourite according to this distribution.