Multiclassing with a Monk?

[incarnate236]

The monk in my game has been complaining lately that the character has become a bit boring since she uses the same ability (Flurry of Blows) every round of combat. She has expressed interest in finding a prestige class or a second base class to shake things up a bit and I was wondering what you might suggest?

So far Psionic Fist and Ranger (Wood Elf favored class) are the only things we have really talked about.

[Grod_The_Giant]

If you want to shake up the combat, you're pretty much going to need to jump into a subsystem. Psionic Fist is a pretty good choice, possibly followed by Slayer; a few levels of a Tome of Battle class would also help, if your group allows the book.

[Person_Man]

What you're describing is the same trap that most Tier 4-5 builds fall into. Limited options get boring, fast.

Suggested solutions:

Let her retrain into a Swordsage or Psychic Warrior or something similar, or use a homebrew Monk fix (there's thousands of them).

Let the player use Pathfinder Monka and Monk Pathfinder Archetypes. In particular, let him "mix and match" abilities (dropping the requirement to trade out every ability in an Archetype) and let him change out abilities at the start of each day.

As a house rule, remove the Attack of Opportunity and Touch Attack step from any Special Attack. In other words, you just make an opposed check in place of an attack roll. This encourages melee classes to Grapple, Bull Rush, Disarm, Sunder, etc. An additional common house rule allows Monks to have full BAB and use their Wis or Dex bonus in place of Str for such checks.

Tattooed Monk or Slime Lord: Gets relatively quick access to Alter Self, which when optimized grants many different open ended options. (You can get extra attacks, some special attacks, fly, burrow, swim, etc). If you use Tattooed Monk, I suggest granting a new Tattoo every level (as opposed to every other level) to increase it's power and versatility.

Shadow Sun Ninja: Waive the pre-reqs to get in, and count the Monk levels as Swordsage levels for choosing the highest level of Maneuvers and Stances known. This will adds Combat Maneuvers and Stances and some nifty special abilities, without the need to completely abandon Monk.

Incarnate 3 or Totemist 2/PrC X: Very multi-class friendly way to add lots of different options that you can change out each day. Though learning the Incarnum rules can be a daunting task.

Warmind: Allows you to get Psychic Warrior powers (plus Sweeping Strike) without the need to go Monk/Psychic Warrior/PrC.

[Failed Phantasm]

I may be reading too much into your mention of Ranger as a favored class, but if you're using multiclassing penalties, it's going to be difficult to make minor tweaks to the existing build without running afoul of them. I also don't know what splatbooks are allowed at your table, so my first recommendation is a bit conservative in that it only requires two additional books, doesn't introduce any new subsystems, and uses the Wood Elf's favored class:

Monk X/Wildshape Ranger Y (minimum 5)/Master of Many Forms 10

This build requires Complete Adventurer and Unearthed Arcana (though the necessary content is also on the SRD (http://www.d20srd.org/index.htm)).

The Ascetic Hunter feat (Complete Adventurer, pg. 105) stacks Monk and Ranger levels to determine unarmed damage progression, so your player won't need to abandon this as a focus of her build if she doesn't want to.
Wildshaping requires at least four levels of this variant Ranger (http://www.d20srd.org/srd/variant/classes/variantCharacterClasses.htm#ranger) (Unearthed Arcana, pg. 58), and while it's initially limited to Small or Medium sized creatures of the Animal type, there's still lots of room for creative use both in and out of combat. The Master of Many Forms prestige class (Complete Adventurer, pg. 58) quickly expands the list of creatures that her character will be capable of wild shaping into, and doesn't have particularly onerous requirements: Wild Shape is taken care of, Endurance is a bonus feat for Rangers, and Alertness is a wash, but it's only 1 feat.

1
If you're allowing all 3.5e content, and if she's really interested in a psionic character, then I'd suggest not Psionic Fist, but Ardent, a Wisdom-based manifester from Complete Psionic (pg. 5-9). This build would be:

Monk 2/Ardent 18 OR Ardent 12/Sanctified Mind 6

It requires the ability to retrain her level 1 or 2 monk bonus feat into Monastic Training [Ardent] (Eberron Campaign Setting, pg. 57), and then taking the Tashalatora feat (Secrets of Sarlona, pg. 119) as soon as possible. Tashalatora will allow all those Ardent levels to advance every Monk class feature of importance, so it's essentially like advancing two classes at once, only Ardent is a full manifesting class and has many more options available than "I punch things". Sanctified Mind (Lords of Madness, pg. 198-203) is a full BAB class that advances Ardent manifesting, and it sacrifices some of that unarmed damage progression, but not so much that it can't be recovered by using a monk's belt (http://www.d20srd.org/srd/magicItems/wondrousItems.htm#beltMonks) or the Superior Unarmed Strike feat (Tome of Battle, pg. 33).