Do you remember when people would tell you they wanted, let you respond and then they could Fuck off happily knowing you both knew what was going on?

Me too. What great days they were!

Here's some times where tact is about as useful as a mouthful of cock when you're trying to sing the national anthem live on TV:

I'm in your way.
You want me to do/say something.
You want me to stop doing/saying something.
I actually annoyed you so much you want to hit me - you know, as opposed to simply hitting me?
You want to have sex with me.
Halfway through having sex with me you realise you'd rather be having sex with someone else.
You were having sex with someone else and thought of me.
You thought you were having sex with me and then realised it wasn't me.
You owe me money.
(If I owe you money shut the fuck up)
If I just offended you.

Seriously, this whole tip-toeing around stuff is tiresome. I recently witnessed a woman in a shop take a good 15 minutes to explain that she wanted a refund on an item. She was so polite about everything, about how she wouldn't normally make a fuss and that she frequents the shop and that she didn't really mind that the item wasn't quite up to scratch and she didn't mean to bother anyone and...

And...

And so I told the cashier the fucking thing was broken and to give her her money back. It took me 30 seconds.

Occasionally there are times where a little diplomacy and tact are needed. In all honesty though, I can't think of any.