Being useful in combat as a face

[Glych]

Basically the title. I'm playing a level 4 phantom thief rogue in a party with a paladin, a cleric and a wizard. I decided to focus entirely on social and out of combat utility.
What I was wondering is are there any magical items, or even non-magical items, that I could use to be helpful to the party in combat? I don't want (or particularly need) to deal tons of damage, or provide exceptional control. I'd just like to have something that can make combat a bit easier for the rest of the party.
Many thanks :)

[Fruian Thistlefoot]

Focus on UMD skill and use Wands/Scrolls to get utility and such.

Low level Tangleburn and Tanglefoot bags are very nice investments till about 6th level.

Caltrops is an easy way to make Difficult terrain if you dont want a wand of grease or entangle. Just making difficult terrain and cutting off a charge is very nice. A grease wand also allows you to help people escape grapples. The Low DC makes it less useful trying to disarm or trip but it can still do plenty of work.

Sound Burst Jars. Very nice items for the lower levels.

Alchemist Fire- I carry a few of these even into High Levels. They are good for swarms and trolls early and is a viable way to start fires quickly if need be. a Group of 4 all throwing Alchemist Fires is a very fast way to down an enemy or group of enemies early levels as well.

[Snowblind]

The best thing I can think of is tossing Tanglefoot Bags and fungal stun vials around. Those are probably the best options. Otherwise, you are probably out of luck. It's very difficult to contribute to Pathfinder combat without magic or feat and ability score investments.

Have you gotten Major Magic and that feat which lets you switch your spell around yet? That's probably your best bet for reliable combat contributions that don't burn GP.

[Cellion]

With how heavy the combat focus is in Pathfinder, you may be in a bit of trouble. Phantom Thief is basically stripped clean of any combat usefulness.

Damage-wise I would either invest in some wands that don't rely on DCs and contain relatively low level spells. Scorching Ray is pretty nice for this purpose, though you might be best served by lower level buff spells like Bless. It'll help your cleric focus on the larger impact spells.
Control-wise I think Phantom Thief works nicely with an intimidate build. The skill unlock for intimidate is very strong if you can get your modifier sky-high. I'd grab an intimidate masterwork tool and/or a Maiden's Helm for this strategy. Alchemical items should also work quite well at lower levels.

[Glych]

Thanks guys, this is exactly the sort of thing I was looking for.
To clarify, my party doesn't mind that I'm not much help in combat. I make everything else less of a headache, which suits them. I was just looking for a way to branch out and at least contribute in combat. All these suggestions fit the bill nicely :)

[Tweedle-Dum]

If you have the UMD for it, you might look at a wand of Ill Omen. 1st level Witch spell, and it has no save...

also, you might check out a whip with a wand of truestrike... it takes two rounds to get it off, but you have a very good chance of disarming weapon users at 15'... Picture the guy pounding on your Paladin - and then you (from behind the paladin) snatch his Greatsword of Paladin Smiting out of his hands.

[Ectar]

Are you an unchained rogue with that archetype? If so, that'd help.
You could try for a bodyguard build.
Requires combat reflexes. Lets you spend an AoO when an adjacent ally is attacked in combat to attempt to aid that ally's AC.
You don't mention race, but it hardly matters. If you're a Halfling I'd recommend grabbing extra traits as a feat and picking the Halfling version of the "Helpful" trait. It makes your aids up to +4, vice +2.
If you aren't a Halfling, you could snag it through the adopted trait, if your racial trait isn't spoken for. And in the case that it is, there's a non-Halfling Helpful trait that gives a +3 bonus when aiding, instead of a +4.

If not, I'd parrot Cellion's suggestion of building into intimidate. Snag the intimidate rogue's edge and you can pretty significantly debuff a group with dazzling display.

[Saldiven]

I also support the idea of looking at Intimidate in combat. Depends on the campaign, of course. If you're going up against mostly undead, constructs, or such, Intimidate won't be very effective.

Against things that aren't immune to fear effects, Intimidate is a decent debuff that allows no saves. You just have to beat the target DC with your skill check. Dazzling Display allows the check to be applied to all enemies within 30' that can see and hear your character.

[Neils Bohr]

I use a lot of these tactics with my bard, and they work well. Just to add a bit.

Whips are awesome, as mentioned above, not only can you disarm and trip, you can use the aid another action at 15 feet.

It's more mundane than tangle foot bags, but a net is really useful, you only need to hit a touch AC, so non-proficiency isn't a huge issue, and it's re-usable.

You can use intimidate to add the shaken condition without any feat, which was hinted at, but not explicitly said. dazzling display makes it better with an area of effect and making it no longer (potentially)language dependent. Adding a wand of blistering invective with your use magic device skill makes it even sweeter, since you insult someone so badly that they burst into flames. (edit: blistering invective gives the an area of effect intimidation as a standard action, instead of a full round like dazzling display, but it definitely is language dependent.)

[SmiloDan]

Use Intimidate and Dazzling Display.

Use Bluff and Improved and Greater Feint.

Combat Reflexes and Bodyguard, supplemented with the Helpful trait.

Tumble into flanking position? To mitigate the paladin's Power Attack attack roll penalty.

From what I understand about the Phantom Thief, you can gain a combat feat every even level with the Combat Trick rogue's talent. You can also select the Major Magic rogue's talent more than once, so you can pick up quite a few 1st level spells. That really opens up your options.

Maybe get Butterfly's Sting and use a (keen) rapier? It's likely your paladin or cleric ally will have better crits than you.

Throwing alchemical items might be fun, too.