4 character builds wanted all 12th level total..

[ARandomGod]

This trick does not work.
Requirements for the Assassin PrC are 4 ranks in disguise and 8 ranks in hide and in move silently.
8 ranks in hide or move silently can only be achieved either by
- a level 5 class with hide and move silently as class skills.
- a level 16 class with hide and move silently not as class skills.
- a level 1 rogue / level 7 wizard

Starting as a rogue you max out disguise, hide and move silently.
Now you have 4 ranks in disguise, hide and move silently.
Move silently and hide are no class skills for a wizard, so he can buy only 1/2 class level ranks. At level 6 (rog1/wiz5) the PC can raise the ranks at maxmimum only to 7 not to the needed 8.

A wizard 5/rogue 1 can achieve 8 ranks in move silently and hide, but he had lost many skill points because of starting as a wizard instead of a rogue.

You can do it, you just end up spending a lot. In 3.5 anyway, In 3.0 I think you'd be right. You will still need a high intelligence to be able to GET that many skills, and you do have to spend a lot (all or almost all)of them meeting prerequisites. But you'll want the highest intelligence you can get anyhow. But yes, you do end up buying several skills at cross skill prices.

However, the assassin's class skills will be very useful in meeting the prerequisites for Arcane Trickster.

Actually, it does.

At least, your objection isn't valid. I haven't checked anything else about it.

A skill is counted as a class skill for purposes of determining maximum ranks if it is a class skill for any class you belong to.

Thus, the maximum ranks in Hide or Move Silently for a Rogue 1 / Wizard 5 is exactly the same as the maxmimum ranks for a Rogue 6 - 9 ranks.

The Rog / Wiz had to spend more skill points to get there, however.

Exactly. You'll have to spend more of your skills on set things, but they're mostly good things anyway. So start at one rogue, then five wizard, followed by one more of a class that grants sneak attack at first level. In the above case I meantioned Assassin, as that's the only pure core option... You'll have a lot more freedom if you take instead one of the Complete Adventurer base classes.

Complete Adventurer has some good options. ... After reading it I think my favorite would be the Ninja. He gets "sudden attack" instead of sneak attack, but it specifically states that sudden attack counts as sneak attack for the purposes of meeting prerequisites such as that. (Sudden attack is like sneak attack in every way I can see with the exception that it does not work from flanking). Additionally, the ninja will get an additional two points of will save, and wisdom added to AC while in light armor or no armor, similiar to the monk's except you're allowed light armor (which the AT will usually not take anyhow). You'd lose the assassin "death attack" and poison use, but I think that's not an issue at all, and you'd loose one or two first level assassin spells. But I think that wisdom mod to AC is completely worth it! Also the ninja gets two more skill points than the assassin, and his class skills include everything you'd need by that point to get into the Arcane Trickster PrC. That's my new favorite build for the AT at this point.
(Rogue 1, Wizard 5, Assassin 1, Arcane Trickster 10, Wizard +3)
Of course, for that you have to be human or elf or something with favored class (wizard).

 

[Patryn of Elvenshae]

Also:

- a level 16 class with hide and move silently not as class skills.

That is incorrect. The maximum ranks in a cross-class skill is exactly half of that for a class skill. Thus, a character can achieve 8 ranks in a cross-class skill at level 13, not at level 16.

 

[Eremite]

(snip) 12th level Monk w/ Vow of Poverty: I think thats it for him? is there any prestige classes worthy of looking into? Or what I think just stay the course with Monk? (snip)

This can work out well particularly if your DM will allow your Wizard to polymorph you into a treant and still keep fighting as a monk. Two "bumps" to your damage dice can make you pretty effective but make sure you get a few protective spells slapped on you.