It's Aaron Ashmore! (Veronica Mars, Smallville, Warehouse 13)
And Eddie McClintock! (Warehouse 13)
Unfortunately I didn't get to see their panel this weekend at Motor City Comic Con but the guys were more than happy to take pics with the fan sign in addition to just being overall awesome with everyone all weekend.
If you don't watch Warehouse 13 you should catch up via Netflix instant and join in on season 4.5 :)
Source: Me and my camera