I'LL TAKE THE CASE!
Special Effects? I run my MIDI Compositions through Synthfont.
Synthfont is an awesome Soundfont and VST (and VSTi) MIDI Player. You also have some cool controls over the notes and some other things.
I use a number of effects on my tunes, for example:
(VST) - BlueCat Flanger Stereo (it lets me do the flanging effects and subtle phasing effects on guitars, creating a nice effect on the background of Dracula's Tears and other tunes)
(VST) - Glaceverb (Lets me set up a virtual room for reverb, echo, etc. with lots of control options)
(VST) - NyquistEQ5 (Lets me set up an analog equalizer that's set up dynamically, sort of like Winamp's iZotope Ozone). It's not bar-driven. It's frequency-driven.
(VST) - Tridirt (Lets me customize my distortions. I use it on my guitars to make them sound different than default stock guitar samples)
(VST) - BloodOverdrive (Lets me customize my overdrive. I often combine it with Tridirt and use it on guitars to give them a little punch)
(VST) - Karlette (Lets me set up panning, delays, and feedback to my electric instruments)
(VSTi) - Sample Tank Pro Audio (A rather large collection of customizable sound samples, with an expanding set if you can find them online. It works with multiple MIDI channels and lets you play with many effects for each instrument. Works best with tracks that have a single instrument, not as well with tracks that have instrument patch changes)
(VSTi) - Pro53 (Native Instruments Waveform Synthesizer - LOTS of nice waveforms and presets)
(VSTi) - DSK (Ok, DSK has instruments all over the place with different VSTi Plugins, including: DSK Brass, DSK Guitars Nylon, DSK Guitars Steel, DSK Overture, DSK Strings, DSK Synthopia 2, and DSK World StringZ - WAY TOO MANY PLUGINS AND SAMPLES hahaha, but when it comes to string instruments, you're covered)
(VSTi) - FM7 (Native Instruments comes through with retro synth sounds)
This, combined with my nearly ridiculously large Soundfont Archive is one of the secrets to my success.
ADDED: By the way, most if not all of these are free plugins. It's just a matter of tracking them down.