Caiman lizard would be my choice. Very cool, rare, impressive animal. Sailfin lizards, water dragons, basilisks, etc. would fit the profile too. Marine iguanas are cool too if you can get a hold of one.
How would you be able to get such a lizard? I herd that a few were kept in captivity a long time ago but all very soon perished. Some were kept in semi-captivity in Galapagos in the research center, but thats pretty much it.
