I found something pretty interesting. I've known about this for a while but decided to test the applications.
Basically, when you EX Guard an A-attack, you're given +2 frames. We all know this. The way I found this out real time is that if I super jumped A'd someone in the air, and they ex guarded the first j.A, I could grab them since they have reduced blockstun.
However, me and Ehrik decided to test further applications of this (and the other way around). What about the player who successfully EX guards (usually on accident). If you are the one EX Guarding (at extremely close range), you can grab your opponent before they can do anything. Thus, if you can react to EX Guard's this is extremely helpful for you. For the defending, EX-Guarding player you can also grab out of 2A/5A on the majority of character hit boxes, depending on the pushback of different characters 5A's/j.A's/2A's (or really just any move that hits close enough for a grab).
Edit: Upon further testing, it looks like you can do any reversal type of move. For example, with F-Koha, after ex-guarding fairly close in the air, I can use magical amber reversal before my opponent can do anything.