$\left|□\right|$ $\left\|□\right\|$ $\abs{-z}$ $\norm{\vec{z}}$ $\left\lceil□\right\rceil$
$\left\langle□\right\rangle$ $\bra{\phi}$ $\ket{\psi}$ $\braket{\phi}{\psi}$ $\left\lfloor□\right\rfloor$
$\left\{□\right\}$ $\left(□\right)$ $\left\lgroup□\right\rgroup$ $\left/□\right\backslash$ $\left\lmoustache□\right\rmoustache$
$\left[□\right]$ $\left]□\right[$ $\left\downarrow□\right\downarrow$ $\left\uparrow□\right\uparrow$ $\left\updownarrow□\right\updownarrow$
$\left[□\right[$ $\left]□\right]$ $\left\Downarrow□\right\Downarrow$ $\left\Uparrow□\right\Uparrow$ $\left\Updownarrow□\right\Updownarrow$
$\left(a\right)\left(\frac{c}{d}\right)$ $\bigl(a\bigr)\bigl(\frac{c}{d}\bigr)$
$\Bigl(a\Bigr)\Bigl(\frac{c}{d}\Bigr)$ $\biggl(a\biggr)\biggl(\frac{c}{d}\biggr)$
$\Biggl(a\Biggr)\Biggl(\frac{c}{d}\Biggr)$ $\left. \frac AB \right\} \to X$
$f(x)=\begin{cases} x/2 & \forall x=2n \quad n \in \Natural \\ 3x+1 & \forall x=2n+1 \end{cases}$
$\binom{n}{k}$