Feel like I've watched just about everything in this genre, I'm a huge fan of sciency shows, especially ones based in space. I'll try to give a list of the major ones I've already watched to the best of my memory.
Already watched/up to date on release;
Star Trek - all series
Firefly
Farscape
The X-Files
Supernatural
Sanctuary
Haven
Warehouse 13
Sleepy Hollow
Alcatraz
Arrow
Smallville
The Walking Dead
Stargate Universe
Fringe
Heroes
Defiance
Buffy the Vampire Slayer
Angel
Doctor Who
Torchwood
Andromeda
Almost Human
Primeval
Defying Gravity
Shows I've watched some of but didn't enjoy;
Marvel's Agents of Shield
A town called Eureka
Helix
Flash
Gotham
Z-Nation
Lost
Battlestar Galactica
Stargate - all other series except Universe
The 100 (might give it another chance)