How would you react?

simply, create a scenario( lets try and think outside the box, here) and the person below will tell you how they'd react in such a scenario. I'll start:
 
Some random guy comes up to you and licks your hand.

I'd advise him he has to buy me dinner first. 
  
The Doctor asks you to be his companion on the TARDIS.

Yes to the power of HELL YEAH!!
  
 
You get donkey punched in the back of the knee's and brutally insulted by a dwarf 

i'd cry, go home, eat a pint of ice cream and reevaluate my life 
 
 
 
Kelly Clarkson pulls up to you in a limo, throws a water balloon full of ketchup at you, calls you a "Vagabond" and drives away into the night

Take a shower and update my status to "F*** Kelly Clarkson"

You're sitting at your computer (or w/e) and a blue midget appears beside you in a ball of green light. He hands you a strange green ring and tells you that you have been chosen to represent the corps at its darkest hour and you are now a green lantern. As the ring touches your finger your clothes change into this:

The blue midget disappears and you're left like that.

I change the channel to my second favorite show, Gilmore Girls, while listening to Danger Zone.

Nuclear bombs around the world go off leaving only three survivors: you, Rosie Perez and Björk.

we would repopulate with the most annoying voiced children in the world
 
your ceiling fan comes alive and chases you

I battle it using the toaster of doom.

Batman comes to you and offers to take you in as his ward, but under the condition that you wear the original Robin costume(yes, the one with no pants) when fighting crime with him.

Break out into an all out death battle! 
 
A hobo won't stop following you until you "pay your dues" but when you question him he refuses to be specific.

i'd give him a dollar (i assume that's what all hobos want out of life)
 
 
You open your closet only to find a 87 year old Vietnamese immigrant hiding there

I facepalm and say "Not again!"

A circus clown tied to a boat anchor crashes through your ceiling.

Take a sip of my drink, look at him, tip my hat, and ask "What's up?"
 
You have the option to be immortal. Doing this comes with all the responsibility of Jack Harkness from Torchwood (plus or minus his omnisexuality; your choice), and you will die very, very often while on the job. Do you take this gift?

Yes, in a heartbeat 
 
You have the option of killing Hitler without any ill effect to the timeline, with all the lives lost during the Holocaust and WW2 being saved but doing so will cause the one person closest to you to be erased from existence and only you will have memories of him/her. 

No, i've learned the hard way to never try and change history...damn Dolorean.... 
 
 
You wake up one morning to find Hugh Hefner on your lawn with the 12 playboy playmate centerfolds of the year 2010, he says you can spend a whole day with all of them, and do WHATEVER you'd like with them, such as play checkers, or charades, but you have to cut off your pinky finger, what do you do??

Join them and have a crazy, best--movie night.

You woke up in the middle of the night, strap in the bed with your best friend standing next to you with a knife, what would you do?

(I can't come up with anything better.)

Tell him that I have a horde of evil toast monsters spawned from my toaster of doom(see above) on the way to kill him, then summon the horde.

A little GREEN midget walks up to you and offers to give you a drug for free that is guaranteed to give you super strength and super durability, but will cause you to go sterile. Do you accept his offering?

I'd take the drug from him, preserve some sperm(Im sure you know how), and then consume the drug, becoming sterile man.
 
A drunk teen just crashed into your brand new lamborghini. He passes out in his own vomit. What do you do?