Power Maul on my archon

I have modelled up my archon with the succubus halberd. http://www.thedarkcity.net/t8277-mordred-bloodyhand-archon-of-the-scorpions-sting#88672

I am thinking about using it as a power maul.....that way i get the str bump and still get to use his initiative.....worth giving a go do you think?

Depends on whether there are a lot of SM players in your local meta or not really. It would certainly be useful to bump off Aspect Warriors or Necrons for example.

So far I am playing against alot of Orks some marines, and will be facing eldar and tau soon.....if i gave him a power axe plus a venom blade he can choose which one he is using yes?

Yes.

Power maul may have place on a Troup Master. Just for giggles.

I foresee a couple of problems with this plan - firstly, you've equipped the model with a halberd, which according to the rulebook counts as an axe. WYSIWYG players might pull you up on this (I wouldn't, but some might, and you would have to make sure your opponent knows what you're intending it to be.) Secondly, the benefits of the power maul are outweighed by the drawbacks. The AP 4 makes it very unhelpful against MEQ, and if you gave your Archon combat drugs he might have plus one strength anyway (plus two with a second pain token). The concussive part is nice as a feature, but next to useless for a character that's initiative seven already - it'll only really be useful against high initiative special characters, ie Eldar phoenix lords, and he won't get through their armour anyway. Any armour that he can cleave through he wants to be inflicting instant death with the hits, making the huskblade the better option (in my opinion). An agoniser is probably better than the maul really, as it lets you ignore more armour saves, and wound bigger stuff.