>>537865131
The turret is from a mod https://www.nexusmods.com/fallout3/mods/5630
You can upgrade its stats and it cycles randomly through various weapon you unlock for it. It also repairs on its own and you can deploy it anywhere.
There's also a crossbow in the mod that has several upgrade slots that work on different enemy types, like explosive-coated bolts, poison bolts, chance to get bolts back after shooting, etc. You can slot in whatever upgrades you want on the fly. It also has a communications module and you find out that there's another person in the wasteland with a turret like you. you both end up following in each others footsteps, but you never meet.
https://www.nexusmods.com/newvegas/mods/37172
The mod author's NV series has its own version, pic related. You can feed her food and other shit guns lol to upgrade her, but she's similar to the turret in function with a bit more personality and can do some unexpected things. Both mods also give you a sort of base area to repair/heal your turret buddies if they hit 0 hp.

It's fun stuff.