Monk 6/Soul Eater 10/Assassin 24 (Bruce Leech)

What this build gives you: 17 pre-epic BAB for 6 unarmed attacks per round (7 with flurry of blows); your unarmed attacks apply 2 negative levels each giving you temp HP each time; enemies you kill with your fists are transformed into level-scaled wights you control; wights explode like a bomb on death damaging everyone around (destruction retribution); can shapeshift into any creature you kill with your unarmed attacks for 24 hours (you can even use their special abilities) giving you a boost to physical abilities and AC; wisdom to AC; flurry of blows; hide in plain sight; 17d6 death attack; true death attack; additional bonuses to strength, dexterity, constitution, saves and skill checks for 24 hours after draining levels.

Weak points: critical-immune and sneak attack-immune enemies must just be beat down, no sneak attack damage boost.  High DR and enemies with immunity to level drain may give you trouble - I suggest always having a good enchanted kama handy you can quickly switch to and deal with those enemies.  Not many options for healing - it is a good idea to get regeneration equipment on this build.  The saves and AC are good in this build, but not as crazy high as I like them to be.

Build Name: Bruce Leech

Race: Githzerai

Alignment: Lawful Evil   
                     
STR 12      
DEX 20      
CON 10      
WIS 18      
INT 14      
CHA 8      
                        
Lvl   Class   
1   Monk 1: Expertise, Lore 2, Hide 4, Move Silently 4      
2   Monk 2: Hide 5, Move Silently 5                  
3   Monk 3: Weapon Focus (Unarmed Strike), Hide 6, Move Silently 6      
4   Monk 4: 19 WIS, Hide 7, Move Silently 7
5   Monk 5: Hide 8, Move Silently 8                     
6   Assassin 1: Alertness      
7   Assn 2                     
8   Soul Eater 1: 20 WIS
9   SE 2: Improved Disarm      
10   SE 3                     
11   SE 4                     
12   SE 5: Corpse Crafter, 21 WIS
13   SE 6                     
14   SE 7                     
15   SE 8: Destruction Retribution      
16   SE 9: 22 WIS
17   SE 10                     
18   Assn 3: OPEN FEAT      
19   Assn 4                     
20   Monk 6: 23 WIS
21   Assn 5: Epic Skill Focus (Hide)      
22   Assn 6                     
23   Assn 7                     
24   Assn 8: Epic Skill Focus (Move Silently), 24 WIS
25   Assn 9                     
26   Assn 10                     
27   Assn 11: Epic Fortitude      
28   Assn 12: 25 WIS
29   Assn 13                     
30   Assn 14: Epic Will, B: Epic Reflexes      
31   Assn 15                     
32   Assn 16: 26 WIS
33   Assn 17: Improved Sneak Attack      
34   Assn 18: B: Improved Sneak Attack      
35   Assn 19                     
36   Assn 20: Improved Sneak Attack, 27 WIS
37   Assn 21                     
38   Assn 22: B: Improved Sneak Attack      
39   Assn 23: Improved Sneak Attack      
40   Assn 24: 28 WIS

Note, this is a great candidate for an undead template like necropolitan (you will need to use Soul Radiance to get a humanoid's form to qualify) for the immunities and getting healed by the negative energy burst when your wights explode.  Make sure to buy off the githzerai level adjustment as soon as you can (level 6 and 9).