No books are banned
Excellent.
I also tend to never get magic items
Is that by choice or because the DM doesn't drop any? (In the latter case, you might consider Vow of Poverty from Book of Exalted Deeds.)
Anyway, I have a few build stubs.
Rogue 3/Barbarian 4/Nightsong Enforcer 10 (skill tank)
That one loses only one base attack in 17 levels and only has one hard feat requirement, and it's a fairly good one: Improved Initiative. I'd also strongly suggest Power Attack. Out of combat you can do trap monkeying and maybe a few other skills, but in combat you fight like a Barbarian. Other good feats are Leap Attack, Improved Bull Rush/Shock Trooper, and Extra Rage. If you go with a charging build, the Neraph race will help you trigger Sneak Attack more often and the Lion Totem alternate class feature lets you pounce. The Rogue levels will also help you hit the prerequisites for the Nimble Charge and Twisted Charge prerequisites. You can top this one off with more Rogue and Barbarian levels or another prestige class.
Spellthief 1/Wizard 4/Unseen Seer 10 (rogue caster)
The only feat this one really requires is Master Spellthief, although even with the high Intelligence you'll want, you may like Able Learner (which requires you play Human or a Human subrace). You're half a spell level behind the Wizard (even with a Sorcerer), you can cast in light armor, and you're only three Sneak Attack dice behind a single class Rogue. If you don't want items like Greater Truedeath/Demolition Crystals, you might consider spells like Gravestrike or Vinestrike for your Advanced Learning. (I'd hold off on Vinestrike until I found out how many plants we were planning to fight, though. Or maybe just get spells that are good against plants and give up on physically attacking them anyway.) Hunter's Eye is another decent pick; it puts you ahead of a pure Rogue on Sneak Attack dice. You might consider a specialist Diviner so you qualify more easily for Metamagic School Focus, then use Persistent Spell with Gravestrike and Hunter's Eye. If you plan on melee, Wraithstrike is another good choice, especially with Extend or Persist. Alternatively, you could just play him like a Wizard and just treat your Sneak Attack like an afterthought. You have a lot of options to top off, like Spellwarp Sniper for attack spells, Daggerspell Mage for TWF, or Arcane Trickster if you don't want to lock yourself into a particular role.
Beguiler 1/Wizard 4/Ultimate Magus 10 (dedicated caster)
For dedicated skill monkeys, this build eats at least three feats: Able Learner, Practiced Spellcaster, and a metamagic feat. (Practiced Spellcaster is there to get 9/10 Wizard casting out of Ultimate Magus.) Beguiler is there for two things. 1: Add a few Wizard spells you know you'll want to cast repeatedly to the Beguiler list. 2: Burn Beguiler spell slots to add free Metamagic to your Wizard spells on the fly. You can top off with any Wizard prestige class. If you want some Master Specialist levels, you could enter at level 5 by pushing Practiced Spellcaster back to level 6 (which works out to the same Wizard/Beguiler caster levels by level 12). You'll need some tricks to get a Persistent Spell out of your Beguiler spell slots (without taking more of a hit than necessary to Wizard casting), but Quicken, Maximize, Fell Animate, Fell Drain, Empower, Twin, and Split Ray are no problem. If you specialize, consider dumping Enchantment and Illusion, since you'll retain access to a lot of them through the Beguiler side. You'll probably want the classic specializations of Conjurer or Transmuter for their wide selection of buffs, save-or-lose, and battlefield control.
I'm sure someone will come behind me and tell you I'm an idiot and this is no way to build a character, but at least here's a springboard for discussion...