I like the look of the metal butt plugs. But not only do I want it to look good for me. I want it to feel good for her. stainless steel or aluminium ? Est
My favourite metal plug is the njoy Pure Plug 2.0 http://www.lovehoney.co.uk/product.cfm?p=12603
It's wonderfully weighty, and it stays put, plus it's perfect for temperature play, especially if you want to chill it to use on one of these hot Summer days. The Pure Plugs also come in 3 smaller sizes if you're not quite up to the 2.0.
Another good metal plug I have is the Metal Worx Teazer http://www.lovehoney.co.uk/product.cfm?p=21923
It's smaller, more tapered, and goes in more easily. It's also rather more prone to slippage if you're not careful. It's a good little plug, but I like it less than the njoy.
I have reviews for a few metal toys on my blog if you're curious: http://incendiaire-reviews.blogspot.co.uk/search/label/metal
Aluminium plugs are considerably lighter than the steel kind, which has its pros and cons - I personally really enjoy the weightiness and 'presence' of a steel plug, plus bonus g-spot stimulation if I use them in a certain way, but prefer aluminium for longer wear and for use during penetrative sex, plus aluminium heats up and cools down faster than steel.
I can't comment on prostate stimulation as I don't have one, but the njoy Pfun plug is shaped exactly for that purpose.