Is there anything really worth buying or is all the stuff worth having found in the game?

What dost thou mean?

Are there any weapons or armor etc. that is worth buying or is all the good stuff "found" ingame through quests etc.

I mostly loot kills. Ammo I buy the rarer types, and even then I usually pay for it trading ammo for weapons I don't use. Weapons/armor for reparing with is about the same- mostly looted, occasionally bought. Now that I think of it, about the only "required" purchases to me are the occasional custom weapon schematic to have all 3.

it depends how you play the game, i buy ammo, mines, grenades, lunchboxes for bottlecap mines, sometimes i buy weapons to repair my weapons, i buy some armor, i find and loot stuff but i also buy stuff from the merchants. i like to equip towns like bigtown, canterbury commons and megaton with armor and good weapons, megaton i just give em laser rifles and assault rifles, but bigtown and caterbury commons get good weapons and armor since those town do come under attack. but i buy quite abit of stuff from the merchants. i buy .44 cal pistols, sniper rifles, chinese assault rifles etc.

So there is no certain Thing that I need to save caps for that only a certain vendor has?That's good to know.I keep thinking of Oblivion that had items in the shops that you couldn't get anywhere else.Also how do you reverse pickpocket?

Have you seen the things you can buy for your house at Moira or Lydia's? There are themes (decorations that are thematic that are installed in your home all at once) and individual items you can buy like a Nuka Cola Machine, an Infirmary, etc. They are pretty pricey. It's not as elaborate as Oblivion. You really can't make decorating your house a significant part of the game, but you can spend a fair amount of caps doing it.

To reverse picpocket someone you sneak up on them, and when you would go to talk to them you are in their inventory and instead of taking something out you would put something in. The tricky part is they treat you as though you are stealing and you lose a tiny bit of karma (-5). So you need to be just as stealthy to do it as you would be if you were stealing. That would generally mean using a StealthBoy in my case. I wouldn't try it without one because I'm usually putting clothing in their inventory and they notice something big like that and it takes a few tries. I've never tried it without one. So save first, approach from behind, it's great if they are sleeping, but you can't always get that, and be prepared to try over and over in some cases.

The most alert NPCs need something like the Chinese Stealth Suit, plus Sneak of 85 (that equals a Sneak of 100 with the bonus from the armor) plus a StealthBoy plus being asleep plus multiple tries. But it can also depend on what you are trying to take from them. You just have to go out and try and not be afraid to experiment and make them hostile at you if you fail. That's what saving first is for With the caravaners, for instance, and giving them better armor, I just put on a StealthBoy sneak up behind them, save and then try a couple of times and slip the new armor in their inventory while they are standing their at their selling locations without much trouble. They're usually pretty easy.

The only thing similar to that in FO3 is the schematics, which vary in price from 600 to 1500 caps or so.

Personally, whenever I hit up a vendor I buy up every scrap of ammo, especially powder-based ammos (.32, .308, .44, 5.56mm, 5mm, shotgun). I'll also buy up every collectible item (blood packs, scrap metal, teddy bears). Occasionally I'll buy up their entire stock of frag grenades, combat helmets (as it's hard to find repair sources for combat helmets), or anything used to make the special weapons. A lot of the weapons sell for more then the cost to purchase the components, so it's a way to make money.

I always keep a stash of loot in my home base, things like pre-war money, pre-war books, scrap metal, teddy bears, laser pistols/rifles, assault rifles, meats, bloods, chems, etc.

Once I have 3000+ caps, I no longer feel the need to take every last thing to the merchant. If I'm going to the merchant to make a 1500 cap purchase, I can always scraqe up enough meats, spare chems, old weapons or armor so that I go to the merchant and get caps back from the transaction. But early on, I'm saluaging everything that isn't nailed down in places like Springvale, Greyditch, Jury Street, etc. Later on, it has to have a 10:1 cap:WG ratio for me to pick it up.

I have some of the furnishings and I got the pre-war theme.What are the teddy bears for?

The only thing I'd add to what Llama said is that if you're trying to reverse pickpocket in order to keep an NPC (such as a caravan merchant) from dying so easily, the items you RPP onto them have to have a higher damage (weapons) or damage resistance (armor) rating than what they already have, or else they won't equip them. So the stuff you give them (e.g. Chinese Assault Rifles, power armor) needs to be in reasonably good condition. And don't forget to give them ammo for their new weapons.

You should give them a few stimpaks as well - they will use stimpaks to heal themselves in combat.

The caravan merchants are fairly easy to reverse pickpocket (or to steal from). At the other extreme is Brick, the Reilly's Ranger with the unique minigun Eugene. I've never tried to steal Eugene from her myself, but I've read posts here from people who have tried, and they've said that even with 100 Sneak, the Chinese Stealth Armor and with Brick sound asleep, they've had to try and retry and retry for two or three hours to get that gun without getting caught.

They're just junk items, really. You can decorate your house with them, or you can use them as ammo in the Rock-It Launcher if you've built one.

If you've finished The Pitt DLC, there's a mini-quest you can do that'll allow you to net some pretty decent caps for collecting them and bringing them to someone.

(yes to the Pitt DLC use of teddy bears) But I also collect every nuka-cola truck that I can find, along with the miniature robot models that some add-ons place in the world. Found a miniature of the Virgo lander this week (added by a mod).

If it's unique, and might look interesting on a shelf, I collect it.