Maybe I'm just being cheesy and nostalgic, but I'd like to see some Mega Man inspired power armor. Zero was kind of a wasteland wanderer type in a later series...
I'd like to see it as the Mk 22 and the regular model 39. I grew up shooting the model 39 and it's still one of my personal favorites. A regular mag only held 8 rounds, but you could really make them count with a little practice.
I loved the NES version of Strider when I was a kid. I've been thinking for a while that it'd be a cool addition to another game I love. A super quick, plasma harnessing sword seems like it would be right at home in New Vegas.