One of my favorite VST commercial plug-ins for recording guitar is the BBE Sonic Maximizer.  This plug-in emulates the actual BBE Sonic Maximizer hardware.  It adds a lot of meat and more punch to your recorded guitar tone.  I will use it a lot if I am quickly recording some ideas for riffs.  If my tone is weak during the recording (which it probably is because I just want to get the musical idea down) I will use this plug in to beef it up. You can also use it in real time if you have a properly set up computer with no latency.

The Sonic Maximizer Stomp Box.  This guy can add a lot of tone to your current set up.  A buddy of mine used one with his Peavey 5150 head because at the time his Tubes were 17 years old!  It did the trick though.

This nifty effect is also available as a rack mount unit.

Hey!  It's good enough for Scott Ian from Anthrax!  So it has to be cool!