An Ordo Xenos Inquisitor. This is an old 'Cobalt-1' mini, with the pistol replaced with an old Legion of the Damned bolter, a scout biker stowed shotgun on the back, and a couple of plastic purity seals from the Tactical Marines sprue. I've always thought the character models from the Cobalt-1 range had a distinctly Old School Rogue Trader look to them (probably because they were scuplted by Bob Naismith, who made a lot of the original Rogue Trader Adventurers).
A long while back, my gang was awarded a Graviton Gun following a successful Loot mission. This conversion represents 'Filthy' Lucre, Patrol Drake's melta gunner, carrying the weapon. I used the same bits as I did on the same character carrying the melta, but made the Graviton Gun from a range of components. The bulk of the gun is the flamer from the Cadian Command Squad sprue, but to give it a real retro sci-fi look appropriate to the weapon, I gave it the coil from one of the power field pylons that came in the Battle for Macragge set.