A couple of my dads, that I have used instinctivly without thought(and thought they were fairly common), But were immediatly loved by other people and incorporated into their vocabulary.
“It’s just another piss in the ocean”
and it’s counter part
“Well I’m not gonna try to piss out a forest fire”
One of my professors said “Useless as tits on a motor.”
He also would say that something that worked out well was “Slicker’n whale snot.” Properly said with a bad fake Maine accent.
Dad was a urologist, huh?
From my mother:
“If ignorance is bliss, that guy must be delirious.”
I think this came from my Grandpa:
“His language was more colorful than a baboon’s ass.”
From Dad:
“Slicker than snot on a doorknob”
“Hotter than a two-peckered goat”
“Well I’ll be dipped in shit”
“Tighter than a camel’s ass in a sandstorm”
Biker motto: if it has tits or wheels, sooner or later, its a hassle.
Closer to shipping sand to the Sahara. Taking something with you that is cheap/free and in good supply at your destination. Newcastle was a popular coaling port. Ideally, a steam ship would throw the last shovelfull of coal on the grate as it anchored at Newcastle.
I used to hear “slicker than snail snot” or “slicker than owl shit”. (Since when is that slick?)
“It’s little of this the Burnses have”
“Boys never make passes at girls who wear glasses”
This one I picked up from some book or another, and I just love it…
“That’s as gay as old Dad’s hatband!”
Now, it seems obvious to me that it dates from long ago in America (along the lines of the “gay 90s”) meaning exuberant happiness, but it fits just as well for other things…
(hijack)
:eek: :eek: :eek: Yes, I grew up in the 80s, and I use the word “gay” to mean stupid or cheesy or however you would define that…
I have absolutely 0% anti-gay bias, and understand how it would be offensive. I’m careful only to use it in private. But you know what - I’m sick of parsing every word I say, and I’ve decided to let this one go. Probably because it’s absurd (to me) that I would be anti-gay.
(/hijack)
Forget where (maybe one of Jim Bouton’s books) but I heard a description of a pitcher as, “He’s so tight you couldn’t pound a toothpick up his ass with a sledge hammer”.
Same vein, I have a friend who always suggests, in a bad neighborhood, “Lock your car up tighter than a nun’s cunt on Easter Sunday”.
What a lot of y’all are posting are metaphors or similes - statements of comparison or analogy between specific persons/things. (Similes use like, as, or than, with one entity to the left of the conjunction and the other on the right. Metaphors are freer in construction.)
Aphorisms would seem, by the above definition - and also by the way I’ve always seen the term used - to be more universal. Not just statements about whale snot or the Philadelphia Eagles or a particular salesperson capable of selling walk-in freezers to Inuit. But truisms. Rules of thumb, meant generally about a class of people or things, or abstractions like love, life, music, art, business, etc.
Shit in one hand and hope in the other, and see which gets filled faster.
Aphorism. Or maybe proverb.
(A proverb is just a very well known aphorism.)
Not necessarily under-used.
Colder than a witch’s tit in a brass bra.
Ah, OK.
Clearly you haven’t been shat on by an owl.
That’s *under-*used? I think it should be forced into retirement. And those bespectacled young ladies should be sent my way stat.
You know how “tight” meant “cool” up to about 4 years ago? (Maybe you didn’t. I wouldn’t blame you.) One of my old high school classmates used to say “tight like prom night” instead. 
Hah, for what it’s worth, I’m not sure you’ll actually have let it go till you don’t want to justify yourself.
Years ago, someone here on the Dope (can’t remember who!) used the phrase:
“If (something good happens), I’ll be crapping in the tall cotton.”
I adored this phrase so much, I’ve since adopted it.
So thank you, whoever you are!
You’re right, but I’m new here, and based upon some of the vitriol that’s spewed, I’d hate to get painted as a jerk until I deserve it… 
“Boar hog” just sounds redundant to me. I’ve also heard it as “tits on a bull.”
Not sure if these are exactly what the OP was looking for, but when my father was thirsty (usually at the end of the workday when it was time for a beer) he’d say:
I’m drier than a cork leg. (Which for the longest time I heard as “corked lake” and couldn’t make sense of)
or
I’m drier than a popcorn fart!
You’re not really helping your case here, you know. (Neither will any further defense, I might hasten to add.)