Shogun 2 Total War Mods
As you know, some of us prefer to mod the game to improve some of the weaker aspects of it.
I will list mods that I found to make Shogun 2 more enjoyable to play.
1)
DarthMod - improves AI, changes speed of the units, fixes diplomacy, doubles unit sizes (e.g. Yari Ashigaru are now 300

), gets rid of AI cheating like spawning units, fixes castle defence, removes projectile trails and Horo's, etc.
I suggest that you play the vanilla game beforehand to make sure that you want to rebalance it - DarthMod will definitely change the feel to the game and make it more old school Total War-like.
2)
Better Unit Cards - changes unit cards and colours so that you can distiguish between different types of units instantly. Doesn't break the game at all and certainly helps the look of it.
3)
Japanese Speech Fix Mod - changes some of the commands in Japanese that were totally misfit for the purpose and make them sound realistic (uses in-game sounds). Certainly recommended for anyone who knows Japanese or doesn't want to learn gibberish by playing the game.
4)
Shogun 2 Music Mod - "This mod changes some of the music in the campaign, custom and Historical battle maps". Nothing more to add IMO, you might or might not like it.
5)
Larger Spawned Garrisons - if you're worried about clans being destroyed in the first turn or find the AI to lack the will of defending their realms, check out this mod, it greatly improves the garrison sizes in the castles.
Not compatible with DarthMod afaik (that one changes these settings in its own way).
6)
Extended Campaign Victory Conditions - if you like the game to last longer. Not sure if compatible with other mods.
7)
Shogun 2 Realism - mod aiming to increase accuracy of the game. Not compatible with other overhauls such as DarthMod.
8)
Shogun 2: All-In-One Mod - compilation of the best (according to the creator) of to date Shogun 2 mods - all compatible with each other. Includes DarthMod.
9)
Realm Divide Mod - early version of the mod that changes Realm Divide behaviour in game. May save a lot of frustration to less experienced players.
9a)
Double Clan Fame for Realm Divide - delays Realm Divide event.
10)
Double Unit Size - exactly what it says, doubles unit sizes. I think Darth Mod uses it.
11)
Clan Color Mod - makes clan colours look more realistic - e.g. not overly bright or cheerful.
There's plenty of others, I'll edit the post when I have some spare time.
I'm using Darth Mod, Clan Color and Better Unit Cards mods atm.