Name a build that does not work in normal games, but rocks in URF
Here are some of mine:
Full AP
Full Crit
Full AP
Full Roflcopter 
What are some of yours?
Here are some of mine:
Full AP
Full Crit
Full AP
Full Roflcopter 
What are some of yours?
Dovahkiin Sion. You shout at people and they die.
AP : utterly busted
Incidentally, AP Blitz and Kog work outside URF in some situations, notably ARAM.
full ap blitz works wonders in normals what are you on about
Rather trivially,
with no mana items
lol
I've seen videos of full AP Jarvan. Flag people to death.
Full move speed Rakan. Ghost + Righteous Glory + Mercurial Scimitar + Ghosblade + Ult. If you guys get Rakan in ARURF, take ghost instead of flash and try that build. Hella fun.
Full AP Pantheon. His W and ult absolutely make it possible. Though I've never ran a full AP Panth on Urf (I use an AP/AD Mix), I've seen it happen. All because of the W.
Point and Click? Check.
1-Second Stun? Check.
100% AP Ratio? Check.
Also the Ult scales with AP as well.
Another fun strategy I use in Dominion and Ascension games that kicks bum in urf is FULL MOVEMENT-SPEED RAMMUS.
Ghost + Luden's + Deadman's + Righteous Glory + Yommuu's + His Q.
Hoooo boy.
And build numero tres: Attack Speed Trundle. Since he can basically keep his W up forever. Not to mention, I build 3 Attack Speed Items and reached 2.5 Attack Speed (The Maximum) without needing to use W. It's insane.
AP Shyvana AP Ashe (can sort of work in aram though)
Magic pen 
Full AP 
Full AP 
+ 
i was able to do 3 circles around their nexus before the tower shot hit me.
they stay where they are because you auto so fast.
Critcrank this build is insanely fun with his w doing double damage
AP shyvanna her e damage is already ridiculous in dragon form might as well go ap to 2 shot someone
AP jhin traps 1 baron 0
Full ap nasus but everyone knows this
all of those "can" work in normals but one that need urf is
rabadons with the rest being tank
my favorite is
with
