The animation for Arming/Disarming the bomb sites on rush should be client-side.

I’m in Australia, so the ping to US West is a little over 200, which means the delay between me pressing arm/disarm and seeing my hand snap to the device is a little under half a second.
When you’re under time pressure this feels frustrating and buggy, I actually thought disarming the bomb was broken and was about to make a bug report until I figured out I just had to hold my hand there and wait.
If the hand-snap is calculated client side (the actual arm/disarm timer can still be server side) then it will feel much smoother and players won’t think it’s buggy.