Charisma doesn't effect dialogue aside from speech checks. Intelligence can effect the dialogue, low INT characters will have access to dialogue high INT characters won't, ande vice versa. There are also other miscellanious speech checks that require various skills, guns, mediccine, etc.
And useless is a subjective term.
Strength - Most of my characters are ranged specialists, the only reason most have 7 strength is to be able to effectively use the heavier weapons. Otherwise I don't get much use out of it.
Perception - Perception at best effects how soon enemies appear on your compass, at worst it does nothing else, save for boosting stats from the get go.
Endurance - Increases the amount of health you have, useful for a lot of obvious reasons.
Charisma - Unless I roleplay a savvy talker, this stat for me is always at 1. I never use it. It doesn't carry the weight it did in the originals. Wasted potential and wasted SPECIAL points for me.
Intelligence - Increases the amount of skill points you get per level, to a maximum of 15 @ 10 (17 with educated), and is needed for some speech checks. One of the SPECIAL stats I use the most.
Agility - Increases AP, decreases reload time. Most of my builds revolve heavily around scouts, snipers, or just a jack-of-all-trades that are of an agile build. I always make it a point to get my character's AGI to 10 from 8 (Agile frame + Implant). I also rarely use vats so, take it as you will.
Luck - Increases Crit chance by 1%/Point for a total of 10%. This is, by far, my favorite special stat. Expecially with the mayhem that it can cause. I have a build for Ruin, where he has 10 luck, and is an EW specialist; namealy, Lasers. He uses Meltdown and Laser Commander (favorite perks) exclusively.
And here is why Luck is my favorite SPECIAL stat:
This build for Ruin revolves around his chance to Critically hit.
10 Luck adds a 10% chance to critical hit.
Add in the trait Built to Destroy thats another 3% for a total of 13%.
Add in the perks Light Touch, (+5%) Finesse (+5%), Laser Commander (+10% with Lasers), and Set Lasers for Fun II (+4% with EW), for a grand total of a 37% critical chance.
Right now we're at achieving Meltdown once every .37 shots.
Now we get into equipment; add in the 1st Recon Beret (+5%), Ulysses' Duster (+5%), and Lucky Shades (+1%) and that turns into a 48% Critical Chance, for a Meltdown almost every other shot.
Now add in consumables and VATS; True Police Stories (with Comprehension for a +10% bonus) while VATS gives a static +5% bonus. That brings us up to a 63% Critical Hit chance, which is just over a crit every other shot. Now; even without true police stories you'll still have a 53% chance to critically hit. Which is still over a critical every other shot.