The most frustrating thing a client can do?

Phone you up and breathlessly say they have just received an important e-mail, and then try to read it out to you.

Er, please forward it to me first...?

Reminds me of an architect who started reading me the outcome of a planning application verbatim over the phone.  Eventually managed to interrupt and get him to read the conclusion and send it to me to read at my leisure.

Spend an hour on the phone with you where you go through a plan and they agree the next steps which they are going to take.  only for them at the end to say "please can you send me a full summary of this by email".

and

When you send them a detailed point by point email that could not be simpler to read / follow / act on  of what to do, they open it and within moments of getting it they immediately ask for a call (clearly not having read it) so you can literally read it line by line to them. 

Something along these lines:

I want to do X

You can't do X under the documents

But I want to do X

Yeah, but if you do X, you will get sued

They won't sue me, I am doing X

OK, but Y will happen and you'll get sued

I AM DOING X

*does X*

*Y happens*

*client is sued*

WHY DID YOU LET ME DO X???!

fook off you little gobshyte and wipe your own arse

I am sacking you

*bovvered faice*

....

Senior managing partner - Wang, I have had a very cross phone call from your client saying you were negligent

In reality, what Davos said.

Day to day though - what everyone else said.

Tom, what do u do now? are u retired? everyone has a client? even if it's just their boss/line manager...

Or a variation:

”If you do X then Y will happen and you get sued”

client does X and Y happens

”What do we do now?”

well buggered if I know, we had options before, now we dont.