If you have a beefy enough system, this macro really makes the game 'pop'.

/console shadowlod 0
/console overridefarclip 1
/console farclip 1600
/console horizonfarclip 6226
/console groundeffectdensity 256
/console groundeffectdist 140
/console smallcull 0
/console skycloudlod 3
/console characterAmbient
/console extshadowquality 4
/console environmentDetail 2

It increases the ground 'clutter' and vegetation and lengthens the draw distance for shadows and models, amongst other things. It also reduces the ambient lighting on your character, so you no longer stick out like a lightbulb in the environment.

If the performance loss isn't worth it, you can revert to default settings with the following macro -

/console shadowlod 1
/console overridefarclip 0
/console farclip 1277
/console horizonfarclip 2112
/console groundeffectdensity 64
/console groundeffectdist 70
/console smallcull 0
/console skycloudlod 0
/console characterAmbient 0
/console extshadowquality 0
/console environmentDetail 1

Also, if you run a multi-core processor, theres a console command you can use to increase the number of threads devoted to model rendering, effectively increasing performance in crowded areas - /console m2Faster (0 - 3, with 0 being no additional threads). The number of threads should correspond to the number of processors/cores you have at your disposal.

so 0 = 1 processor, 1 = 2 processors, etc?

Or just type in the actual number like 2 for an intel dual core processor?