Mentioned this in another thread, so I thought I would get the ball rolling. This thread is to post what war and skirmish games you've played with a simple pro/con list. Kind of a quick overview of what people have played and what they like/don't like about it. Try to keep Pros & Cons to games you've played, but impressions of a read through are always good. I left all the collectible games off my list for brevity, but please feel free to include them if thats your main game!

Warhammer Fantasy Battles/40K
PRO: Large player base. Handles large battles well. Well developed background. Tons of different kinds of units to choose from with lots of personality.
CON: Many immature players. GWs "our models ONLY" rule. Higher model price. Fixed army lists. IGOUGO gameplay. GW Stores.

Mordheim
PRO: Detailed skirmish combat. Experience/campaign system. Free expansions.
CON: IGOUGO gameplay. Untested warband lists. Fixed warbands lists.

Gangs of Mega City 1
PRO: Command system. Detailed skirmish combat. Experience/campaign system.
CON: Little to no support. IGOUGO gameplay. WtF saves make it possible to lose in the first round. Somewhat limited gang selection.

AT-43
PRO: Fast gameplay. Lots of personality. Pre-painted models. Alternating activation.
CON: Very slow expansion. Rules read like a foreign language.

5150
IMPRESSION: Great idea for a game, but feels half done. Their is no attempt at a real point system. Scenario based ONLY. Great campaign system. Great reaction system.

No Quarter/No Limits
IMPRESSION: Sounds and feels good. Similar to WHFB/40K but wide open for whatever minis you want to use. Activation system looks interesting.

Song of Blades and Heroes
Have not read yet, but very interested.

Ill add to the list. Here are a few that I know personally.

Heroclix
PROS: Quick, easy to learn game based on popular superheroes. Stats and powers are shown on a click base. Santioned tournaments supported by Wizkids with prize support.

CONS: Certain Super-Rare figures are incredibly unbalanced. Quality has decreased in recent sets as the prices are going up. Superheroes means super immature players. Lots of misprints on base or characters cards which calls for lots of Erratta.

MechWarror
PROS: Quick, easy to learn game based on the ever popular BattleMechs from BattleTech. Once again a clickable base helps track figure stats and special equipment. Mechs can be upgraded by adding more equipment or Veteran Pilots.

CONS: Does not have the depth of Classic BattleTech. Has been declared a stagnant game business wise and Wizkids is no longer making new sets. This also means no prize support for tournaments. You would have to be a fan of the genre to know what MechWarrior is.

I have yet to play a real game of Star Wars Mini's. I will probably post some pro's and con's on that later.

Thanks Gilbert! Thought of a couple others to add to the list.

HeroScape
PRO: Simple to learn. Fast play. Pre-painted. Great looking battlefields. Lots of variety of minis.
CON: Battlefields can take forever to set up. Fixed figure selection. May be TOO simple for some.

D&D Minis 2.0
PRO: Large user base. Familiar system. Tactical depth. Alternating activation.
CON: Some VERY bad paint jobs. Not fully compatible with D&D Minis 1.0. Broken character combinations. No rules for real 3D play.

Axis & Allies Minis
PRO: Lots of tactical depth. Nice pre-painted armor. Fast to play. Minis good for other 15mm games.
CON: Unrealistic battlefield scale. Troop pre-paints so-so. Old armor models too small and ugly.

I will echo everything Gilbert said about HeroClix. Great summary of the game!

Infinity:
PRO: Amazing model sculpts, Reaction rules in IGOUGO framework. Skirmish level (<12 minis usually to play). Cheap starter sets. Free rules on their site. Dealy combat.
CON: No scenarios in rulebook. Minis are on the expensive side. You'll be lucky to find opponents. Or even stores that stock it. Requires *lots* of terrain. (not a problems for WWG customers but bears mentionning)

Stargrunt II:
PRO: Free rules, great dice system, various figure scales. generic rules not tied to a miniature line.
CON: No points levels, rare to find any opponents. Feels like sci-fi vietnam instead of sci-fi.

Defiance: Vital Ground:
PRO: Generic rules not tied to a miniature line. Army list creation rules. Cheap rulebook. Armies are build similarly to 40k-ish games.
CON: No way you'll find opponents. Army list creation takes a while.

Heavy Gear Blitz (or L&L):
PRO: Giant Robots! Faster rules (compared to older versions of the rules). Canadian/Montreal company Asymmetrical victory conditions. Alternating activations.
CON: Abusable army list creation system. Expensive rulebook. Most figures come in 2-packs (while squads are generally 5-units although there are basic squad packs of 5 as well). Little to no opponents or stores stocking it. Funky scale (n-scale 1/144) for a wargame.

Dirtside II:
PRO: 1/300 scale (or smaller) for big battles, Alternating activations. Free Rules.
CON: Point system very abusable. Little to no opponents

Starmada:
PRO: Generic space rules. Very good starship construction system (hard to abuse). Not tied to a miniature line. Cheap rulebook.
CON: Hex based movement/ranges.

WARMACHINE:
PRO: Great Figures. Cheap starter packs. Simple system. Giant Robots! Easy to find opponents. Army list abuse encouraged. (Play like you have a pair!)
CON: Lots of special abilities to memorize, can get expensive if using lots of infantry. Minis are steadily climbing in price. Ego-crushing defeats very likely the first couple of games.

Warlord
Pros: Beautiful figures, stats degrade with damage, plays well from small to fairly large armies, Reaper listens to player feedback
Cons: Printed rulebook is horribly out of date, hard to find players in some areas

Cav
pros: Stompy Robots, stats degrade with damage, lots of depth, combined arms, plays faster than Battletech (pro for me, at least), chunky figs
Cons: NO printed rulebook, hard to find players

Warmaster
Pros: Really big feeling battles, exciting combat, nice models, free rules, good game of maneuver and command
cons: hard to find figs and opponents

Started looking at Defiance and it sounds like something I would be very interested in. Thanks!

No Quarter/No Limits
PROS: Absolute freedom and control over army/unit creation and composition (nothing is "illegal" so long as it fits within the overall game rules). Alternate unit activation creates more dynamic/strategic gameplay options. Activation points system allows for infinite flexibility in terms of unit actions order.

CONS: Micro-management can slow-down gameplay. Does not handle large battles well. Vehicle rules (No Limits) still in need of refinement. Intial effort required to scratch-build armies may put some people off (although several sample armies already exist).

Dont forget:

Necromunda:
PRO: Skirmish battle game with great established background, rules are free on specialist game site, great opportunity to use World Works platform command set. Wonderful campaign system.

CON: Any successful hit pins for a turn (gets really annoying), sometimes one gang starts to dominate a campaign and needs to be retired, official figures have to be ordered direct from GW.

Bloodbowl:
PRO: Campaign System. Medieval fantasy football. Bloodweiser babes. FREE rules. Not really tied to a miniature game line. 10 tons of fun. Perfect for Arenaworks
CON: No longer supported by GW. Rare to find opponents in North America. Sucky GW models are mailorder only.

Victory At Sea:
PRO: WWII Naval wargame. Not tied to a miniature game line. Inexpensive rulebook. Simple rules use the ACTA game engine. Campaign rules. Inexpensive models available from all over the world. Force allocation system is unbalanced.
CON: Basic rules have problems, fixed in expansion (another purchase). Simple rules use the ACTA game engine. Force allocation system is unbalanced. Spotty support.

(Some items are in the pro and con section on purpose depending on your likes or dislikes)

General Quarters 3:
PRO: WWII Naval wargame. Very tight ruleset. Realistic ranges. 2 types of Campaign systems. Scenario driven. Inexpensive models available from all over the world. Knowledge of WWII naval tactics / battles rewarded by ruleset.
CON: No points system of any kind. Expensive rulebook. Realistic ranges mean a large playing area required. Only available from publisher. Clunky purchasing process.

Monsterpocalypse
Pros: Good Rules, Prepainted, nice backdrop and background
CONS: "COLLECTIBLE" (BOOOOOOO)

AT-43
PROS: Well thought out rules, quick play, beatiful prepainted figures
CONS: Translation of Rules sucks at times, not all units have been released, packaging can cause players to own more mini's than they need.

Confrontation: Age of Ragnorock
PROS Nice ruleset, quick play, prepainted figures
CONS Translation of rules sucks at times, not all units have been released in PPP, some metal units were not included, prepaints not as hot and sexy as AT-43 as far as quality and detail.

Gangs of Megacity one
Pros Nice ruleset for both ranged and Close Combat, well thought out traits, nice reaction system, metal mini's released for the game are awesome.keeps to the spirit of the Judge Dredd universe
Cons plastic mini's released for this game suck massively, no longer supported by Mongoose