Here's a stab at some of those abilities...
Hopping Charge (Ex): A gronk may make a leaping charge attack to deal double damage with its headspikes. A gronk may move any direction, including vertically, as part of this action without making a Jump check.
Illuminated Rage (Ex): A gronk exposed to sudden bright light (such as any spell with the light descriptor) flies into a berserk rage on its next turn, fighting madly until either it or all its opponents are dead. It gains +4 to Strength, +4 to Constitution, and –2 to Armor Class. The creature cannot end its rage voluntarily.
Nearly Deaf (Ex): A gronk is almost completely incapable of perceiving sound, and is nearly immune to language-dependent effects and sonic effects dependent on hearing. As a result, a gronk gains a +x racial bonus on all saving throws against such effects, and if the effect deals damage, suffers no damage on a successful save and only half damage on a failed save. The creature has adapted to this limitation and thus suffers no penalty on initiative checks because of its deafness.