SciFi Actor Cameos

I was thinking about how many of the shows on SyFy (sic ) use actos from others scifi shows in cameo or recurring roles, and even how some pick up actors from other shows that have ended to round out their casts (SG1 did both, fairly often!). How many can we name here?

hmm...
Jewel Staite and Sean Maher (from Firefly) played a couple on an episode of Warehouse 13
Paul Blakthorne (from Dresden Files) played a businessman on a Christmas episode of Warehouse 13
There were also some star gate actors whose names i can't recall who were also featured on warehouse 13 for an episode or two...

Eureka had Wil Weaton for a couple episodes
(and i'm sure several others i'm not thinking of...)

Sanctuary picked up several stargate actors for an episode or two.

Thanks. Warehouse 13 has had a lot of them, and Eureka is getting a fair share.

Ben Browder & Claudia Black are two from Farscape that made a good fit on SG1, each for their own reasons and not least because they both switched the types of roles they were playing.