Creating a Planeswalker?

[Sezdrin]

So I've recently become obsessed with the idea of a charismatic thief who travels from plane to plane for the sake of high adventure, swashed buckles and for the chance of pilfering them of their valuable goods. The only problem is that I've been trying to think of Prestige Classes that lend well to the concept. The only one that I can find is the Horizon Walker from the DMG. Are there any others that can help me achieve this kind of character?

[Bad Wolf]

Hellbreaker? From Fiendish Codex II. Devil-flavoured, but works well with outsiders.

[VariSami]

Jaunter from Expedition to the Demonweb Pits (p. 172) is the closest parallel, I think. Other than requiring the Spring Attack chain of feats, it is also very easy to qualify for. Gatecrasher from Manual of the Planes (p. 27) does not move between planes completely freely before 9th level in the class but might also qualify.

[atemu1234]

Anyone with a magic item of use-activated Plane Shift?

[Karmea]

Amulet of the Planes? (http://www.d20srd.org/srd/magicItems/wondrousItems.htm#amuletofthePlanes)

[ZamielVanWeber]

Planar Champion from Manual of the Planes could work. Their 9th level is the ability to open a hole to/from the Astral once a day, so you can move pretty freely, albeit slowly.

[DrMotives]

A better fit from Manual of the Planes is Gatecrasher. They get planeshift as a spell-like once per day at 9th level, and the class description is almost exactly what you laid out you wanted. They're skillmonkeys with class features either related to opening portals they shouldn't be able to, or sweet-talking to angry examplars they run across, or surviving the normal environmental features of whatever plane they find themselves on.

[Ruethgar]

Jaunter is what I'ld go with. As long as you are a creature that dreams you've been to at least one other plane already. Get etherealness somehow before level 2 and you can go jaunter from there. I would suggest Bloodlines and Uncanny Trickster to boost your Travel Power a bit.

Martial Monk
Flaw: Dodge
Flaw: Mobility
Monk: Spring Attack
First: Educated