None of this will be in the vanilla game, but, I think some of this would make for nice modding material.
Plus, is there ever going to be a Half-Life 3? Doubtfully any time soon, so, why not add some old familiar love to a new game world like Fallout 4, especially where it could plausibly fit, and also add in some game play elements not present in the vanilla incarnation?
Weapons
1. Bugbait - In Half-Life 2, there was a grenade-like weapon called bugbait or antlion pheromones. This weapon summoned a few pesky antlions to follow you around, and attack anything you threw the pheromone ball at. The antlions could burrown and fly short distances, so, almost any enemy anywhere was game, and, the little buggers respawned if killed, giving the player a constant group of about 3 antlions to attack anything and everything.
Plausibility for Fallout - there's mutated everything in Fallout. Why not have some antlions from Half-Life, and the pheromone ball to control them? Antlions were some of the best companions ever; better than some wasteland dogs.
2. Hivehand - In the first Half-Life, there was a creature full of bees, or wasps that you put on your hand, and it shot bees or wasps that automatically homed in on a target, even if they were hiding behind something. The bees or wasps, or whatever would also auto-generate inside the hand, so, you never ran out of ammunition, but, you would have to wait for the ammo to regenerate.
Plausibility for Fallout - it could be an FEV experiment? Do we need much plausibility to shoot bees at enemies?
3. Gravity Gun - You know it. You love it. Turn anything in the environment into a weapon and launch it at an enemy.
Plausibility in Fallout - There's already the junk gun that shoots teddy bears and stuff. Why not a gravity gun that basically does the same thing?
Enemies
1. Barnacles - Barnacles in Half-Life would hang on ceilings with their sticky icky tongues out, and catch the player by surprise whenever they stumbled into them where they'd get pulled up closer and closer to a hungry mouth, unless the player shoots and kills the barnacle before getting to the mouth.
Plausibility for Fallout - Mutant stuff! Plus, it'd add some fun and interesting additional atmosphere to caves, and dark places.
2. Antlions - these cheeky bugs were relentlessly persistent about attacking anything that stepped on sand in their territory. With the pheromone gland, they could be controlled, but, without the pheromone gland, they were a bullet sink because they'd spawn 3 or 4 at a time, and be on infinite spawn until you got out of their territory.
Plausibility in Fallout - These things were more challenging than cazadores, but, also, they could be controlled with the pheromone gland thing, and with mutations everywhere in the Fallout wasteland, what's to say antlions couldn't exist?
3. Headcrabs - headcrabs were a little bit like the alien facehuggers from aliens, but, instead of gestating a baby alien inside the victim, the headcrab turns them into a headcrab zombie. These hoppity hopping critters were quite pesky, and I think would also be a fun addition to the Fallout universe.
Plausibility in Fallout - Radiation. Mutants. Why not?
These additions, I think, would add some more fun to the game outside the conventional everyday "hey look, I modded just-another-real-world-gun-into-the-game" standard, or the "hey-look-I-reskinned-the-animal-that-already-exists" standard mod, which are all fine for some real-world variety added into the game, or making existing models look more interesting.
Anyway; thoughts?
Thanks.