Latin as an economical language: my favourite Latin expression is

Malo malo malo malo.

Latin students will be familiar with its meaning.

Another favourite of mine is this palindrome and magic square:

S A T O R
A R E P O
T E N E T
O P E R A
R O T A S

(Sator arepo tenet opera rotas). The translation is a bit dull, but whoever thought of it was clever.

For translations of these, and a few others, try this link.

Latin Tongue Twisters