Are there any great electric guitar VSTi's? What are you using, if any?

Personally I find AAS Strum Session too fake sounding, unless it's very hidden in the mix.
 

Glyn Barnes
Checkout Orange Tree Samples they have a large range of acoustic and electric guitar libraries for use in the free Kontakt player. 
 
I would say that for general use the Rock Standard or Stratosphere are probably the best (Les Paul, and Strat respectively) Strawberry is also a good all-rounder but they are all different and good. They all have a good range of articulations and setting up the velocity switching is easy.
 
Apart form the "lead" sounds The strum sequencer is intuitive and quite versatile.
 
They are sampled clean and use Kontakt's effect and amp sims for maximum versatility. You can also bypass the effects and use your favourite amp sim(s). Multi-track mode allows for up to 4 discrete outputs if you want to get adventurous.

A good choice - for Electric guitars also check out:
 
Shreddage 2 by Impact Soundworks
Electri6ity by Vir2
RealStrat / RealLP by MusicLab
Amplesound guitar series
Native Instruments Session Guitarist Electric Sunburst
 
Orange Tree as mentioned by Glyn are probably the best, but also very pricy. Personally I went for Shreddage 2 as it was the best bang for buck at the time (I got all 3 models in a bundle for $99).
 
Amplesound's range is great for acoustics, and also IMO the easiest to play.
 
A word of caution though:
1. Most of these require the full version of Kontakt
2. Although these emulations sound fantastic, covering every technique you could imagine, the learning curve is huge. Unless you're a wiz in the piano roll editor, it'll take you ages to get the results in their demos. In most cases I've resorted to practicing on an actual guitar and playing it myself... cos it's quicker!
3. The in-built effects while adequate aren't that great. You'll probably want some other guitar rack suck as GuitarRig5/Amplitube/Revalver/Overloud. This is down to taste - I tried them all and I tend to go for Overloud, which I upgraded from the CW verson to the full version.
 
For more immediate results (if somewhat more limiting) also look at the VirtualGuitarist series by uJAM. This I do use regularly as it's so easy to get a great sound right away if I just want strumming or basic power-chord riffs.
 
Like I said, the learning curve for most is huge - not that they're hard to use, just hard to get good results without lots of editing and tweaking. I guess this gets quicker with practice.
 
What I personally do for stuff I can't play (like crazy fast sweep picked scales), is use a combination of Revalver's pickup modeller and Overloud and:

• Model my own guitar with Revalver
• Model Shreddage 2 with Revalver
• Play most of my parts using a real guitar
• The bits I find impossible to play, do with Shreddage
• Run both the modelled guitars into a bus, with Overloud on the bus... they sound like the same guitar

M.