Get the light "racing" model... that way when you drop it on your toe, it won't hurt so bad. :redneck:
We have two... one is a craftsman "SUV" jack that does the one pump to lift height thing, and the other is some off-brand that I can't remember. It has a lower overall profile, and has a twist handle for controlling the valve vs. the screw type... I use both, but I like the off-brand one because it has a larger cradle... convenient for lifting a rig by the diffs and it also doubles as a ghetto transmission jack... as long as there are enough helpers to balance it.