I notice the second knife is just held in the other hand uselessly, not actually doing anything. No offense, but that kind of takes away the appeal.

I'd like to suggest perhaps letting that second knife have its own animation for a Crit. Otherwise, it just looks like dead weight- and not even in a way that's funny, IMO, or else I'd be complimenting the detail.

On that note, I'd like to suggest that this Crit animation be a quick stab with said second knife, rather than a slash. Anime and martial arts movies might purport otherwise, but thrusts/stabs are generally far deadlier than slashes, and so they make more sense than a slash for a Crit, at least for blades this size- and while I know TF2's comical and cartoonish, it also does have *some* semblance to realism, at least in that a stab would be much more in-character for the universe as a Crit animation than just another slash.

Also, a stab with the off-hand knife would in my opinion simply be much more gratifying than just another slash.