Arguendo, ceteris paribus, res ipsa loquitur. Vel non.

Bryan A. Garner's (editor in chief of Black's Law) What's hot and what's not.

Garner believes that if the latin phrase has a clear English translation and is not a legal term of art it shouldn't be used.

Here's is a what's hot; what's not list for 2009.

In
habeas corpus: “you have the body.” Written orders for bringing someone into a court, most frequently related to ensuring a person’s imprisonment or detention isn’t illegal.

res ipsa loquitur: “the thing speaks for itself.” A rebuttable presumption of negligence.

respondeat superior: “let the superior make answer.” A principal or employer is liable for the acts of an agent or employee within the scope of agency or employment.

corpus delicti: “body of a crime.” Physical evidence of a crime and objective proof a crime has been committed.

Out

Arguendo: use “for the sake of argument”

inter alia: use “among other things”

ceteris paribus: use “other things being equal”

sua sponte: use “on its own motion”

ab initio: use “from the beginning”

vel non: use “or not”