whats the message exactly? That the one who wears that shirt is so devoted to training legs that he sees them equal to death and taxes? Because it does not apply in general, death and taxes are certain for everyone but you can live your whole life without training legs...
If I'm going to wear an ironic t-shirt related to lifting it won't have the words "leg day" on it. It's kinda stupid because "leg day" is probably the most commonly skipped day amongst people that would call it "leg day".
I've always liked the Iron Mind shirts myself, nice and simple. The Squats being the Breakfast of Champions one is my favorite.
One of these days I'm going to get around to making a shirt that say "DO MORE DEADLIFTS" and another one with Jaunty's "Kill It" flowchart on it.