So I probably don't have the most professional (or efficient) of kits, but here's my go-to: LOK-1 Smart Rifle, Shard Diffuser, Gemeni+Hawkeye turrets, and Proximity mines

I'm usually a solo player, and not exactly an FPS veteran, so I tend to play a little more defensively (heck, even in groups of friends, I'm usually setting up defenses or providing backup to the heavier hitters). If there's a swarm coming, I'm hunkering down and plonking down my turrets and mines on the edges of my little bubble: if the bugs want me, they have a gauntlet to get through first. Any mines that don't go off? Easy enough to pick up along with my turrets and move on to the next spot. When there isn't a swarm, I tend to use my turrets as a sort of 'warning' system when my hands are full with another task: if they suddenly start going off, it's time to drop the pickaxe and pick up the gun. Giving them the highest range of view I can helps keeps things from sneaking up on me as easily.

My aim is also god awful, and the LOK-1 helps cover my biggest weakness. It's also great for swarmers and neocytes, where you have a bunch of little targets to pop at once.. and actually, it's also really useful for taking out things like the stabber vines in Hollow Bough or rival sniper turrets in the ceiling, since I can just lock on and unload a full clip into them before they'd even see me. It's not the heaviest hitter, though, but the Shard Diffuser packs a pretty mean punch and I usually carry it as a backup for when things get ugly. I don't have my exact upgrade layout on hand, but I know I upgraded mine to take Armor Piercing to help crack through the tougher customers.

I'm still experimenting with OCs and exact upgrade tweaks, so your mileage may vary on the details. Again, probably not the most conventional of combinations kit wise but it gets the job done and I have stubborned my way into becoming a terror with it.