Comprehensive list of Champion Niches/Themes (WIP)
I made a list using every champion in the game to try to clarify the strategic or gameplay reasons you pick one champion over another in champ select. I am very open to feedback and encourage anyone reading this to leave comments with your opinions and suggestions.
ASSASSINS (High burst damage and mobility, usually low to no defense)
Sustain Assassin (High endurance through extended teamfights)
Bruiser Assassin (Most survivability, no escape)
Utility Assassin (Large breadth of non-damaging abilities)
Flanker Assassin (Has tools to sneak behind enemy lines and break their formation)
Escape Artist
Anti-Mage Assassin
Premier Cleanup Assassin (Poster girl for finishing off a low health enemy team)
Single Target Assassin
Juke Assassin (Has potential to outsmart enemies while being chased)
Poke Assassin (Low CD, long range damage abilities)
Ambush Assassin
Opportunity Assassin (Capitalizes really hard on enemy mistakes)
AoE Assassin
Trap Assassin
Outplay Assassin (Relies on mechanical skill and timing to get clutch kills)
MARKSMEN (Ranged damage dealers that primarily use autoattacks for high sustained damage)
Utility Marksman
Zone Control Marksman (Denies areas with threat of damage/CC)
Magic Damage Marksman
Skirmish Marksman (Crushes short trades)
Poke Caster Marksman (Casting focused, delivers long range low CD damage)
Anti-Assassin Marksman
Fighter Marksman (Capable of delivering sustained melee damage or burst ranged damage)
Cleanup Marksman
Chase Marksman (Sticks to target, slight engage potential)
Support Synergy Marksman
Sustain Marksman
Premier Hypercarry Marksman (Weak early game, insane late game)
Mobility Caster Marksman (Casting focused, enables kiting/chasing)
AoE Wombo Marksman
Map Mobility Marksman
Run-at-you Marksman (Augments team engage or escape)
Siege Hypercarry Marksman (Safely secures neutral objectives)
Assassin Marksman
Siege Caster Marksman (Casting focused, enables safe and long range damage)
Duelist Hypercarry Marksman (Strong in 1v1s)
BURST MAGES (Delivers high burst from range using casted abilities on low cooldown)
Kite Burst Mage (Damages enemies while escaping)
Engage Burst Mage (Reliably starts fights)
Premier AoE Burster (Highest AoE burst combo, lowest in class utility)
Wombo Combo Burst Mage (Synergizes with AoE oriented teammates)
Zone Control Burst Mage
Pick Burst Mage (Selects a single target for death)
Global Presence Burst Mage
Single Target Burst Hypercarry
Adapting Mage
DOT MAGES (Delivers sustained damage from range using casted abilities, still capable of bursting)
Zone Control DPS Mage
Hypercarry DoT Mage
Anti-Siege Mage (Prevents grouped enemies from taking objectives)
Duelist Mage
Window-of-Power Mage (Has clearly telegraphed moments of potential)
Kite DoT Mage
Self-Healing Tank Mage
Disengage DPS Mage (Peels enemies off of allies/herself)
POKE MAGES (Delivers bursts of damage from a safe distance)
Aggressive Poke Mage (Plays in the frontline instead of backline)
Utility Poke Mage
Zone Control Poke Mage
Burst Poke Mage
Siege Poke Mage (Toolset allows pushing and objective control)
UTILITY MAGES (Focused more on CC and breadth of abilities than damage)
Close Quarters Mage
Magic Damage Enhance Mage
Anti-Melee Mage
Pick Utility Mage
Aggressive Utility Mage
LIGHT FIGHTERS (Melee, usually mobile DPS character reliant on one or two abilities providing brief but massive safety)
Revive Fighter
Duelist Fighter
Hypercarry Fighter
Utility Fighter
On-Hit Light Fighter
Undying Fighter
Skirmish Fighter
BRUISERS (Melee DPS character that uses a mix of CC, mobility, and durability)
CC Bruiser
Pick Bruiser
Zone Control Bruiser
Ranged Bruiser
Utility Bruiser
Flanker Bruiser
Tenacity Bruiser
Teamfight Bruiser (Effective at forcing teamfights and tanking multiple enemies)
Mobility Bruiser
Visibility Blocker
Anti-Carry Bruiser
Assassin Bruiser
Disengage Bruiser
Anti-Physical Bruiser
Scouting Bruiser (Has abilities that reveal distant areas of the map)
Endurance Bruiser (Wears enemies down using sustain and damage)
AoE Bruiser
DoT Bruiser
Savior Bruiser (Bails out one ally from certain death)
Anti-Tank Bruiser
Pure Melee Bruiser
Single Target Bruiser
Sustain Bruiser
Wombo Combo Bruiser
Oppurtunity Bruiser
JUGGERNAUTS (Melee DPS character with mild CC and mobility, also reliant on durability)
Meat Grinder (Scales harder the more enemy champions there are in melee range)
Anti-Carry Juggernaut
Pick Juggernaut
Drain Tank (Gets tankier by doing damage)
Hypercarry Juggernaut
Premier Neutral Objective Control
Summoner Juggernaut
DAMAGE TANKS (Melee, don't have high CC, rely on AoE damage, DoT, and/or durability)
Goes where he pleases (Can't be peeled, can't be deterred by zoning)
All-Rounder (Has damage, CC, healing, utility, AoE, durability, engage, disengage, etc.)
AoE Damage Tank
Kite Tank
Engage Damage Tank
CC TANKS (Melee, uses AoE CC ultimate to engage fights and lock down key targets, low damage high durability)
Hypercarry CC Tank
Anti-Mage Tank
Pick CC Tank
Premier Counterjungler (Effectively invades enemy jungle and secures camps)
Anti-Physical CC Tank
Damage CC Tank
Telegraph Tank (Signals high threat of damage and CC before casting)
Sustain CC Tank
TANK SUPPORTS (Focused on enabling friendly DPS champions while standing in the frontline)
CC Tank Support
Pick Tank Support
Dedicated Babysitter (Most protection, gives least utility)
Engage Tank Support
Anti-Pick Tank Support
Aura Tank Support
Utility Tank Support
UTILITY SUPPORTS (Focused on enabling friendly DPS champions from a safe position)
Roaming Utility Support
Premier Disengager
Premier Buff/Debuff
Premier Utility Support (Has widest variety of buffs, CC, engage, disengage, healing, etc.)
Aura Utility Support
Premier Healer
Savior Utility Support
EDIT 1: Yorick moved to bruisers from damage tanks. Light fighters added. Master Yi and Tryndamere moved to light fighters from assassins. Aatrox, Fiora, Jax, Kayle, and Yasuo moved to light fighters from bruisers.
EDIT 2: Mages reordered into burst, DoT, poke, and utility from burst and control. Fiddlesticks, Karma, and Zyra moved to utility mages from utility supports. Lux moved to poke mages from utility supports. This wiki page gave me a lot of insight that spurred the changes: http://leagueoflegends.wikia.com/wiki/Champion/Champion_Attributes
EDIT 3: Jhin added to Marksmen. Yorick moved to Juggernauts from Bruisers. Shen moved to Bruisers from Tank Supports. Swain and Zyra moved to DoT Mages from Utility Mages. Viktor moved to Burst Mages from Utility Mages. There have been multiple G&B posts made by Rioters further distinguishing Fighters into different groups. If the trend continues to the point of classes being officially announced, I will repost this list with the new ones.