This is a thought experiment PC I did once. At the time he was a member of every class in the game at 30th, though there have been more classes added since then. I think it actually gives you a decent, playable PC, though picking powers and feats a little more carefully for actual play would be a good idea:
====== Created Using Wizards of the Coast D&D Character Builder ======
Jack, level 30
Half-Elf, Bard, Resourceful Magician, Eternal Seeker
Bardic Virtue: Virtue of Valor
Pact Initiate: Pact Initiate (dark pact)
Eldritch Blast: Eldritch Blast Charisma
Student of the Sword: Student of One-Handed Weapons
Seeking Destiny: Keeper's Prescience
FINAL ABILITY SCORES
Str 13, Con 22, Dex 13, Int 16, Wis 14, Cha 26.
STARTING ABILITY SCORES
Str 10, Con 14, Dex 11, Int 13, Wis 12, Cha 16.
AC: 38 Fort: 37 Reflex: 35 Will: 40
HP: 179 Surges: 13 Surge Value: 44
TRAINED SKILLS
Arcana +23, Diplomacy +30, Bluff +28, Acrobatics +21, Streetwise +28, Insight +24, Religion +23, Nature +22, Heal +22, Dungeoneering +22, History +23, Intimidate +28, Thievery +21
UNTRAINED SKILLS
Endurance +22, Perception +18, Stealth +17, Athletics +17
FEATS
Bard: Ritual Caster
Level 1: Arcane Initiate
Level 2: Combat Virtuoso
Level 4: Pact Initiate
Level 6: Student of Artifice
Level 8: Blade Initiate
Level 10: Arcane Prodigy
Level 11: Versatile Master
Level 12: Initiate of the Faith
Level 14: Acolyte of Divine Secrets
Level 16: Initiate of the Old Faith
Level 18: Spirit Talker
Level 20: Disciple of Divine Wrath
Multiclass Mastery: Warrior of the Wild
Multiclass Mastery: Student of the Sword
Level 21: Multiclass Mastery
Level 22: Religious Dabbler
Level 24: Divine Channeler (Paladin)
Level 26: Soldier of the Faith
Level 28: Berserker's Fury
Level 30: Sneak of Shadows
POWERS
Acolyte of Divine Secrets: Astral Wind
Arcane Initiate: Storm Pillar
Bard at-will 1: Misdirected Mark
Bard at-will 1: Guiding Strike
Dilettante: Virtuous Strike
Divine Channeler (Paladin): Divine Mettle
Initiate of the Old Faith: Pounce
Religious Dabbler: Hand of Radiance
Seeker's Lore: Adjure the Chosen
Spirit Talker: Spirit's Fangs
Bard encounter 1: Shout of Triumph
Bard daily 1: Slayer's Song
Bard utility 2: Inspire Competence
Bard encounter 3: Dissonant Strain
Bard daily 5: Song of Discord
Bard utility 6: Ode to Sacrifice
Bard encounter 7: Deflect Attention
Bard daily 9: Wail of Anguish
Bard utility 10: Mantle of Unity
Bard encounter 13: Earthquake Strike (replaces Shout of Triumph)
Bard daily 15: Wall of Sound (replaces Slayer's Song)
Bard utility 16: Iron-Hide Infusion
Bard encounter 17: Strand of Fate (replaces Dissonant Strain)
Bard daily 19: Prismatic Explosion (replaces Song of Discord)
Bard utility 22: Storm Body
Bard encounter 23: Sound Strike (replaces Deflect Attention)
Bard daily 25: Sculpt Fate (replaces Wail of Anguish)
Bard encounter 27: Chaos Infusion (replaces Earthquake Strike)
Bard daily 29: Wyrm Form (replaces Wall of Sound)
ITEMS
Ritual Book, Dynamic Dagger +6, Wand of Witchfire +6, Deathcut Starleather Armor +6, Stormwalker's Cloak +6
RITUALS
Comprehend Language, Glib Limerick