As the title says, what can you steal from someone with Sleight of Hand? I find it a little bit confusing as to its limits. Firstly, the appropriate rules text:
If you try to take something from a creature, you must make a DC 20 Sleight of Hand check. The opponent makes a Perception check to detect the attempt, opposed by the Sleight of Hand check result you achieved when you tried to grab the item. An opponent who succeeds on this check notices the attempt, regardless of whether you got the item. You cannot use this skill to take an object from another creature during combat if the creature is aware of your presence.
The bold part is relevant, the rest is just rules as to how Sleight of Hand works. Now, it just says "something" and that's not very helpful. For instance, can I steal an item they're holding in their hand, or does it need to be on their person?
The only other part of the rules which gives us any indictation as to limits is the DCs, which says:
DC20 : Lift a small object from a person
Okay. Does that mean I can only take small objects? What is a small object? Does that mean I can rob the clothes off a pixie but not the shoelaces off a giant?
One last piece of text from the Sleight of Hand rules:
You can hide a small object (including a light weapon or an easily concealed ranged weapon, such as a dart, sling, or hand crossbow) on your body.
Aha! Some examples of a what a "small" object is. Does this mean I can rob someone's light weapon from them, but not anything larger or heavier? What about a wand? Or a rod?
You cannot use this skill to take an object from another creature during combat if the creature is aware of your presence.
You cannot use SOL in combat. For this you need the 'Steal Combat Maneuver'. This maneuver has his own rules for stealing items and gives penalties for well stored items. The rest is up to the GM. A small good visible item, stored on your cloth / girdle etc. should be the normal target of a SOH attempt. Maybe your GM allows to steal other items with a penalty to your SOH check but it should be impossible to steal someones pants (see steal combat maneuver).
Items that are simply tucked into a belt or loosely attached (such as brooches or necklaces) are the easiest to take. Items fastened to a foe (such as cloaks, sheathed weapons, or pouches) are more difficult to take, and give the opponent a +5 bonus (or greater) to his CMD. Items that are closely worn (such as armor, backpacks, boots, clothing, or rings) cannot be taken with this maneuver. Items held in the hands (such as wielded weapons or wands) also cannot be taken with the steal maneuver—you must use the disarm combat maneuver instead.
Our Arcane Trickster collected Component pouches from opposing wizards in combat. Since the GM had house ruled you had to have them to cast spells unless you had EMC, a feat ONLY Sorcerers could get in that game, her thefts could easily swing a fight on a single roll. Opposing Rogues started tying it, but I carried something like 8 (Str limit). The most I every lost in a melee was 3.