I am currently playing as the Black legion, but I am just kind of getting bored with them and want a new army, so I have beseeched the bowels of Warseer for advice

Imperial Guard: They are my number one choice right now, simply because of the whole "just soldiers" and awesome armor choices. Also, I can expand my army into the Catachans or the Tallarn raiders if I want.

Eldar: Second Choice, but still a contender for my buy. I like the firepower and look of the vehicles.

Dark Eldar: I would choose them if they had more selection and they were a more organized force than a bunch of feuding, sadistic cabals. While I know they are coming out with a new codex for them, I want the new army NOW.