Before the major civil war that consumed Rapture prior to the events of the first BioShock, the original line of Plasmids, ADAM-based genetic superpowers, were designed not as weapons but as fun little enhancements to your everyday life. Every Plasmid had an intended marketed purpose around the household or elsewhere, and at the start of their distribution, some Rapture residents made proper use of them.
Of course, things eventually descended into a horrifying genetic arms race where new Plasmids were designed with the express purpose of killing people, but we're not talking about that right now. Right now, let's look at the first game's Plasmids purely through the lens of practical application.
7 Hypnotize Big Daddy - Bodyguard On Demand
It's admittedly not clear when the Hypnotize Big Daddy Plasmid was developed, or for what purpose. The Big Daddies were supposed to be guarding the Little Sisters while they recycled loose ADAM, so why either Fontaine Futuristics or Ryan Industries would make something that pulls them away from that work is a head-scratcher.
Even so, when Rapture was on the verge of the civil war and Splicers were already lurking about, you probably didn't care too much about whom you had to conscript into keeping you safe. Hypnotize Big Daddy may only provide a temporary bodyguard, but he's a rather effective one that's guaranteed to get you where you need to be safely — assuming you don't do anything to incur his wrath after the effect wears off.
6 Security Bullseye - Mess With Machines, Protect Your Stuff
One of Rapture's most predominant problems was that every single aspect of its public services was privatized, even the police, and those who couldn't afford their services were left in the lurch. The copious amounts of security tech were intended to keep everyone safe, but they couldn't exactly be relied upon to keep you safe precisely when you needed it.
Security Bullseye's ability to control the security drones worked as a quick panic button for when someone was menacing you or taking your stuff, but Rapture Security was either too busy or too expensive. It was also quite popular with the kids, who would use the Plasmid to command the drones in the same way you'd play with an RC car. Hey, when you live at the bottom of the ocean with a bunch of snooty adults, what else is a kid supposed to kill time on?
5 Insect Swarm - Bees Make The World Go 'Round
Insect Swarm was originally created for Rapture's farming enthusiasts, such as the tree managers in Arcadia and the produce sellers in the Farmer's Market. While the idea of manufacturing bees inside your own body is one of the absolute worst kinds of nightmare fuel, it is an objective fact that bees are a vital component of the modern human lifestyle. Without pollination from bees, plants die off, and the few plants Rapture had were vital cornerstones in the production of fruit, vegetables, and let's not forget oxygen.
Prior to the invention of Insect Swarm, Arcadia's managers had to manually distribute pollen through directed air currents, which is extremely ineffective. Without a steady supply of pollen, Rapture would slowly suffocate, and since Andrew Ryan would never condone retrieving bees from the surface, well, they gotta come from somewhere, and that somewhere is your left hand.
4 Incinerate - Melt Ice, Show Off
Incinerate was one of the very first Plasmids developed by Fontaine Futuristics, probably because they knew it would look the flashiest in front of a crowd. Since Rapture was constructed in the 40s, all the home stoves were gas ranges, so Incinerate provided a handy way of lighting the stove on your own (putting aside the fact that a gas stove in an enclosed bubble of oxygen is an absolutely terrible idea, of course).
Additionally, it was marketed toward showoff guys who wanted to make themselves look cool by lighting cigarettes with a snap of their fingers. Its most practical application was for the mechanical staff working in the depths of Rapture, where unheated pipes would regularly freeze due to ocean water. A quick snap and the pipes are flowing again, if only temporarily.
3 Electro Bolt - For Safe(ish) Electrical Work
In spite of the incredibly advanced technology that made up Rapture's infrastructure, stuff was breaking all the time. The city's majority population of snooty entrepreneurs always ensured there was a shortage of mechanically-minded maintenance staff.
In order to make up for the lack of manpower, Electro Bolt could be used to start generators or temporarily disable machines and systems, halting any problems until a repairman could arrive. You could also use a minor dose of Electro Bolt to remotely power small electronics like lamps. It's kind of like the Clapper, except you have to stick a giant needle in your arm to use it.
2 Winter Blast - Cool Drinks, Freeze Food
You'd think, what with so many frozen pipes around Rapture, there'd be plenty of cooling options available, but for every frozen pipe, there was an overheating furnace in near-equal measure. Winter Blast, in a similar vein to Electro Bolt, provided a quick and easy solution for the maintenance staff to cool down overheating equipment in a hurry. Besides that, though, Winter Blast was also a big help in preserving Rapture's various food supplies, with the employees of businesses like Fontaine Fisheries making extensive use of it.
Rapture did have fridges and freezers installed, but it saves a lot of money on the electrical bill when you can just stick a bunch of food in a closet and freeze it with your hands instead of running a refrigeration mechanism all day. It's worth noting that the ice produced by Winter Blast was water-based and safe for human consumption, as opposed to the toxic dry ice produced by its BioShock Infinite counterpart, Old Man Winter.
1 Telekinesis - Everyone's Favorite Superpower
In just about any setting with superpowers, you can't get much more practical than good ol' fashioned Telekinesis. Not only does the ability to move stuff with your mind effectively give you a third hand to pick stuff up, but it also allows you to move things that would normally be too heavy like large furniture. Trying to vacuum the floor of your home but can't get under the sofa? Lift the whole sofa up! Telekinesis could also be used to safely lift and move potentially dangerous objects, from something mundane like a hot coffee pot to something... less so, like a live grenade.
Dr. Suchong once noted in his test trials that Telekinesis could, theoretically, even be used to catch bullets, it's just that most humans don't have the kind of reaction time necessary to do so. That was something the researchers had to learn the hard way.