Front raises with hammer grip "dumbell vertical" not horizontal. I like em
^^ that
And if it gets boring, use a plate with two hands and do "steering wheels".
Grab a plate and hold it at 9 o'clock and 3 o'clock. Raise it, arms outstretched, in front of your face so that you can see your eye in a mirror through the hole. Turn the plate 90 degrees left, then back to center, then 90 degrees right, then back to center and lower the plate. Repeat but make the first turn to the right, and
keep alternating your beginning with right/left turns. This isn't a traditional steering wheel, where the weight is held continuously in front of your face while turning, it's a combo of a front plate raise and a steering wheel, but the 'steering' part doesn't allow you to cheat because you *have to* hold the weight at the top of the movement, and looking back at your eye through the hole via a mirror ensures you keep strict form.
The semi-static hold you have to maintain while turning it left to right gives a serious burn and pump for me. I also feel it a bit in my upper traps.
If you don't have access to a gym and plates, grab any small child that's handy and about the right weight. Kids LOVE being manhandled and tossed about as long as you say "wheeeeee" a lot.
[edit]: Found a video that shows the movement:
http://www.youtube.com/watch?feature=player_detailpage&v=JCD3OTK8Mas#t=51s