I really like the Pilot Pentopia and it is the one I carry most often, it comes with a pen, .5mm pencil and PDA stylus. The pen is a full size ink pen and not one of those mini ones that writes a little then dies

The Pentopia has a very solid metal body but is not very heavy. I like the little levers that you push down to select you pen/pencil/stylus as they are color coded for easy selection (think of the bic 4color multipens) I hardly ever use the pencil but it is nice to have and there is an eraser under the top cap.
My second favorite is the pilot Dr Grip duo and I think both pens use the same ink refill, the duo is my second fave as it is bigger and heavier though the rubber grippy section is real nice.
You can google but styluscentral has both, have tried quite a few stulus combo pens but these two are the best IMHO. You might look at the cross stylus refill as it fits any pen that takes that style refill and you can convert a pen to a stylus and the writing tip feels the best of any stylus replacement, it has more drag to it than the plastic tips do and feels more like natural writing.
