My favorite Sound Design Plug-Ins
In this day and age there are loads of different plug-ins to choose from. There's a huge variety of them that can help you achieve different tonal qualities in sounds and help you create some really other-worldly sounds! Here are some of my absolute favorite plug-ins that I use on a daily basis.
Dehamuniser 2 by Krotos

Dehumaniser 2 is one of the most powerful tools I've had the pleasure of using. I very frequently have to create a lot of monster/creature sound effects in a relatively short amount of time. Thankfully I have Dehumaniser! You can easily throw this plug-in on a mono/stereo track and record your own performance to match picture perfectly for what you're working on. The quality in the sounds are shockingly incredible. It's a little pricey for the Dehumaniser 2 version ($399), but thankfully they have a Lite version ($49) as well. This is an extremely powerful tool and lots of options to create very custom creature vocals. Be sure to check out their website HERE.
DUST by Soundmorph

Where do I begin with this plug-in?! DUST is a synthesizer plugin based on a real-time particle simulation, where each particle is a separate granulating sound source. The motion of each particle is determined by the flow field, which determines the force applied to each particle at each point. This is a VERY in depth plug-in that can create some very interesting sounds. It can be triggered by audio files within your DAW or by a MIDI keyboard. I use DUST quite a lot when working on Lost In Oz to help create new and exciting magical elements for different characters throughout the series! Although this is a very powerful tool, be cautious when you're creating sounds as it does drain a lot of your computers resources. Be sure to checkout their website HERE.
SoundShifter Graphic by Waves

This plug-in is probably one of my most used. There isn't a whole lot too it, but it helps me in so many different ways. SoundShifter lets you change keys, change tempos, change durations, and manipulate the time-pitch continuum with unmatched accuracy and clarity. Being able to pitch up/down while retaining the speed/length of a file is very powerful! The normal price of this plug-in is $149, but there are deals happening all the time that drop the price to $49 so be on the lookout! Be sure to checkout their website HERE.
Fabfilter ProR Reverb by Fabfilter

Fabfilter ProR is (in my opinion) THE only reverb you need. I'll add this on big whooshes, explosions, fly-by's or anything that I need to create distance and a sense of space with whatever environment I'm working with in my project. The UI of the plug-in is very easy as well; they have little popup windows to help you navigate within the plug-in if you're unsure of what each parameter does. At $199 it's pricey, but it's money well spent! Be sure to checkout their website HERE.
Fabfilter ProQ2 EQ by Fabfilter

Lastly, but certainly not least is the Fabfilter ProQ2 EQ. I've been eyeing this plug-in for quite some time and I recently pulled the triggered and purchased it and I'm SO happy that I did. Coming in at $179, this is the one tool that you'll probably use the most when mixing/mastering sound effects and Fabfilter has nailed it with this tool! I can't praise Fabfilter plug-ins enough! They should be in every sound designers arsenal.