From science fiction writer Maureen McHugh on SFF.net, here are a list of handy Latin phrases:

Non calor sed umor est qui nobis incommodat.
It's not the heat, it's the humidity.
<p>
Di! Ecce hora! Uxor mea me necabit!
God, look at the time! My wife will kill me!
</p><p>
Estne volumen in toga, an solum tibi libet me videre?
Is that a scroll in your toga, or are you just happy to see me?
</p><p>
Cum catapultae proscriptae erunt tum soli proscript catapultas
habebunt.
When catapults are outlawed, only outlaws will have catapults.
</p><p>
Lex clavatoris designati rescindenda est.
The designated hitter rule has got to go.
</p><p>
Te audire no possum. Musa sapientum fixa est in aure.
I can't hear you. I have a banana in my ear.
</p><p>
Sentio aliquos togatos contra me conspirare.
I think some people in togas are plotting against me.
</p><p>
Antiquis temporibus, nati tibi similes in rupibus ventosissimis
exponebantur  ad necem.
In the good old days, children like you were left to perish on
windswept crags.
</p><p>
Caesar si viveret, ad remum dareris.
If Caesar were alive, you'd be chained to an oar.
</p><p>
Quantum materiae materietur marmota monax si marmota monax materiam
possit materiari?
How much wood would a woodchuck chuck if a woodchuck could chuck wood?
</p><p>
Nihil curo de ista tua stulta superstitione.
I'm not interested in your dopey religious cult.
</p><p>
(At a poetry reading)
Nullo metro compositum est.
It doesn't rhyme.
</p><p>
Non curo. Si metrum non habet, non est poema.
I don't care. If it doesn't rhyme, it isn't a poem.
</p><p>
Quomodo cogis comas tuas sic videri?
How do you get your hair to do that?
</p><p>
Feles mala! Cur cista non uteris? Stramentum novum in ea posui.
Bad kitty! Why don't you use the cat box? I put new litter in it.
</p><p>
Romani quidem artem amatoriam invenerunt.
You know, the Romans invented the art of love.
</p><p>
(At a barbeque)
Animadvertistine, ubicumque stes, fumum recta in faciem ferri?
Ever noticed how wherever you stand, the smoke goes right into your
face?
</p><p>
Neutiquam erro.
I am not lost.
</p><p>
Hocine bibo aut in eum digitos insero?
Do I drink this or stick my fingers in it?
</p><p>
Vah! Denuone Latine loquebar? Me ineptum. Interdum modo elabitur.
Oh! Was I speaking Latin again? Silly me. Sometimes it just sort of
slips out.
</p>