Do not use the glyph of death strike right now if you are frost or unholy (it's fine if you're blood) there is a glitch where if you take that glyph and have tundra stalker or RoR, it decreases the damage your death strike does. I still own the glyph and I'm hanging onto it until they fix it.
That said glyphs you want:
Plague strike glyph - every spec uses PS, this would benefit you regardless of what you do.
Death strike - again, every spec uses death strike, though keep in mind the bug above
Horn of Winter - this is the ONLY minor glyph worth a damn in PvE
Goul - If you're unholy, this is a good one to get, it's also somewhat decent with other specs if you frequently use your ghoul.
I don't care about PvP glyphs because that's not my focus. Other glyphs are nice, but they require you to be a certain spec and would require you to buy whole new glyphs if you changed specs.