Identify a species which is not a Bronsted acid but a Lewis acid

Bronsted defined an acid as a substance, which has a tendency to give a proton $\left(\mathrm{H}^{+}\right)$, on the other hand, Lewis proposed an acid as a substance, which is capable of accepting a pair of electrons. $\mathrm{As} \mathrm{}_{3} \mathrm{H}^{+}$, $\mathrm{NH}_{3}$ and $\mathrm{HCl}$ has $\mathrm{H}^{+}$ions, these are Bronsted acids whereas $\mathrm{BF}_{3}$ is an electron deficiet molecule, thus be have like a Lewis acid, i.e., electron pair acceptor.