Dihedral group of order 8: $D_{8}=\langle r,s: r^4=s^2=(rs)^2=1\rangle$ (also commonly denoted $D_4$)

E

The quaternion group: $Q_8=\{\pm 1, \pm i, \pm j, \pm k\}$ with multiplication given by $i^2=j^2=k^2=ijk=-1$ and usual rules for multiplying by $\pm 1$.