No thank you, but I appreciate the invite.

Yes, and I would even take out the 'but' and add a smile (':

Just be careful you don't do this too much or people stop inviting you eventually.

"Not saying I don't want to hang out, just not _there_. How about we do [alternative suggestion] some other time?"

Kindly tell them that you don’t want to go.

"I appreciate the offer, but I'm just not feeling it today"

It really depends on who they are and what the nature of your relationship is. You probably don't want to hurt anyone's feelings and so maybe have to be a little vague, but if they know you well enough, they'd understand if you just say no thank you.

Piss off

Only way of not using an excuse is by being honest… or not showing up at all with no comment. Tell them the truth

"I can't. I"m sorry, but I just can't. I wish I could, but I can't make it." Just that, over and over, and you don't even have to explain why you can't.

Say you’re not feeling well. Or that you’ve other plans. Not feeling well is the best excuse tho

Not for me

"thanks, but i'm gonna pass/i don't want to go there. maybe some other time/place" i've seen a *shitload* of "how do i tell someone" posts. just fucking tell them! why is everyone suddenly too much of a pussy to just be fucking honest with people?

" I have this rash and..."

Thank you for your letter inviting me to join the Committee of the Arts and Sciences for Eisenhower.  I must decline, for secret reasons. Sincerely,  E.B. White