That moment where one or both of the fighters just goes into crazy mode? I was watching the ufc ultimate knockouts and this clip reminded me why chuck liddell is so awesome.
http://www.youtube.com/watch?v=_sfWlEztlyA
I know vitor has one and dan severn has that famous moment.
Any more i cant think of?
Rothwell vs vera
wand vs yuki kondo
lauzon vs gabe 
Devlin - Rothwell vs vera
wand vs yuki kondo
lauzon vs gabe
hahah that rothwell moment was great.
i just watched that wanderlei one. the head stomps were scary back then.
lesnar at the beginning of cain fight
him charging at cain like a bull and then flying kneeing him and double legging him to the mat
Anderson vs okami 
Hughes vs Trigg 2 - post nut shot slam
Wand vs Rampage 1
Wand vs Stann
Wand vs Fujita
Wand vs Cung Le
Wand vs Jardine
Wan.......Aww fuck it, lets just say "Wanderlei Silva's career".
Frye,/Takayama
These aren't Berserker moments, but are rage induced.
Ryan Gracie after beating Oyama.
Rampage/Wand in the ring after the Randelman defeat.
The Coleman/Chutebox brawl after Shogun's broken arm.
Vitor being hoisted up by his entourage after his victory in "the beginning"
Tank/Duarte and the T-shirt
Ken verbally thrashing Tito after the Mezger defeat.
Not to derail, just reminiscing...
Frye vs Takayama...both went apeshit.
Ok you beat me, Sims vs Mir
And the entire Dan Henderson vs Fedor fight
My love for you is like a truck berserker, would you like to making fuck berserker!
willienugget -But man does diego have a chinSergio88 -
Diego didn't land a single punch in either exchange.
Boetsch vs okami
Marquardt vs Gouveia comes to mind
Botesh (spelling) vs Okami has to be up there, he was losing that fight badly before he flicked the switch
Frye - Takayama....as tough as it gets...