Telesales (does this count?)
I spent a few month being unemployed a few years back (insert Scouser joke here). What I found quite quickly is that you get an awful lot of telesales calls during the day. Out of sheer boredom, I started trolling these people, rather than just hanging up.

I used to take great delight in:
giving a rediculously false name (Miss Tallulah Nahasapeemapetilon, Rev. Dave Thelordisoursavior)
giving my address as cell 962, B wing, Styal Prison
continuing my conversation with my cat, asking her opinion on what I was being sold
saying "you'll have to speak more slowly, I'm naked"
giving a few fake details, then saying "what is it you want the info for again?" giving a few more fake details then saying "what is it you want the info for?"
when asked if I own my home, saying "no I just squat here"
answering every question with "stop messing about, Dave, I know it's you"
I would always tell double-glazing types that my house didn't have any windows and that I'd bricked them all up because "I'm a vampire, you see"
saying "can you hang on a minute" and lying the reciever on the table, returning every minute or so to say "I'll be with you in a tick"
Asking really stupid questions, like "what's a loan?" or "what are windows?"
just repeating their questions back to them instead of giving an answer

I think I got blacklisted after a while, since the sales calls stopped...
(ScousersPet, Mon 23 May 2011, 15:29, 12 replies)

just got one from some ambulance chasers
"we've been told that someone at your address has had an accident recently"
"no they haven't"
"by recently, we mean in the last 3 years"
"no they haven't"
"try to remember, i'm sure they have"
"no they haven't"
"could i speak to someone else who lives there and ask them?"
"no, i'm the only one who lives here, i think i'd know if i'd had an accident."
"oh. have you had an accident in the last 3 years?"
"no i haven't"
*hangs up.*
( Smash Monkey lowering the tone of the whole internet, Mon 23 May 2011, 15:39, closed)

You've reminded me
"have you had an accident in the last three years?"
"yes, but I was very excited and nursey cleaned it up straight away.
(ScousersPet, Mon 23 May 2011, 15:41, closed)

arf!
got one laughing a few weeks ago.
"have you had an accident recently?"
"yes, i fell off the stage in a nightclub because i was pissed."
( Smash Monkey lowering the tone of the whole internet, Mon 23 May 2011, 15:44, closed)

I got one of these
And got the same thing 'are you sure?'.

It royally pissed me off, I was fuming. How stupid did they think I was? Of course I haven't had an accident in the last there years. I'd remember. How fucking stupid do you think I am, I mean, if I had had an accident so bad that it would leave a paper trail that an ambulance chasing lawyer could follow enough to track me down by it I'd remember. It would need to be something like falling down in a corporately owned building and splitting my head open and waking up in the back of an ambulance like I did that time...oh...

Still, I am not sure would qualify. I don't think they compensate people for walking down concrete steps with their shoelaces undone while drunk off their face on vodka and cheap cider.
( scarpe We Stole Bikes, Mon 23 May 2011, 15:46, closed)

probably not
i think the "are you sure?" is supposed to mean "can't you make up something vaguely believable?"
( Smash Monkey lowering the tone of the whole internet, Mon 23 May 2011, 15:51, closed)

I haven't had any of these in a while - but I find that claiming to have been decapitated in a car crash generates a lot of excitement on the other end of the call...

Bonus points if you can last longer than my record of two minutes before laughing so hard that you have to hang up. Extra bonus points if, as once happened, they ring back to find out why you hung up (and you laugh a lot more).
(Nicklock, Mon 23 May 2011, 16:05, closed)

best one ever
"yes, i've had an accident! i've just tripped over a loose carpet track, running to answer the phone to you! aaarrg, i think i've broken my leg! i'm going to sue you!"
*hangs up*
*phone rings*
"are you ok?"
*laughing fit*
( Smash Monkey lowering the tone of the whole internet, Mon 23 May 2011, 16:11, closed)

Not had the "pleasure" of a call yet.
But the excreta have sent me text messages. I half wish they would call me so I could tell them to fuck off home and hang themselves -- because they're obviously so fucking pathetic the only job they can get is to try to con people into using a shite legal service.
(Me, I'm not... in any way intoxicated, Mon 23 May 2011, 17:23, closed)

Back when Brown was PM
My dad, in a surprising show of quick-thinking for him, told a cold caller they had the wrong name and that he was really Mr. G. Brown but he was very interested in the exclusive phone deal they had for him.

His address?
'10, Downing Street, Westminster... sorry I can't remember the post code though.' Apparently he could hear the keyboard clicking away as they swallowed it, and promised to send him more details in the post.
(sanity challenged, Mon 23 May 2011, 21:12, closed)

Apparently I may be entitled to £3650 for an accident I had.
So sayeth the text message I received today.

It'd be nice if they let me know what the accident was first.
( flake has nothing against your right leg, Mon 23 May 2011, 21:51, closed)

Haaaa! And I thought I was the one who'd had that there "accident"!
I thought I was Spartacus ;)
( blaireau69 , the Cumbrian Travis Bickle., Tue 24 May 2011, 0:21, closed)

In the states you can tell these calls due to the 3 second pause
That I suppose is from the auto-dialer. Takes all the fun out of it when you can't just launch straight into your routine. Although I laughed when my austere other half recounted how by sheer logic she maded a telemarketer whimper after he asked her forf her credit card info for the "free" cruise she had just won.

I could have warned him, and saved him from the withering pains of death with which I am all too familiar.
( BrokenCoccyx doesn't mind if you grope on, Tue 24 May 2011, 8:53, closed)