Since there's apparently this horrid fear of people learning how to actually block, here's a full list of all the moves in the game that are unblockable. These are ones that set up a stun and usually take some charge-up time. Currently, nothing else in the entire game is unblockable. I have personally tested every single move against a block in Practice, both aerial and grounded.
Kratos - Helios Flash Charged. (Down Circle)
Parappa - None.
Fat Princess - Scepter Bash Charged. (Square)
Sweet Tooth - None.
Colonel Radec - None.
Sly Cooper - Cane Swipe Charged. (Down Square)
Nathan Drake - None.
Cole MacGrath - None.
Evil Cole MacGrath - None. (Charged punch only stuns if it hits, doesn't break guard.)
Ratchet and Clank - Sonic Eruptor Charged. (Triangle)
Jak and Daxter - Wave Concussor Charged. (Down Circle)
Big Daddy - Incinerate Charged. (Circle)
Dante - None.
Heihachi - None.
Nariko - None.
Raiden - Heavy Combos Charged. (Triangle)
Sackboy - Jetpack Corkscrew Charged. (Forward Triangle)
Sir Daniel Fortesque - Hero Sword Thrust Charged. (Forward Square)
Spike - Double Stun Dash Charged. (Forward Square)
Toro - Fiery Mochi Charged. (Oni Style, Triangle.)
Notice how all of them are the charged versions. Each of them take a full second.