Lacrosse ball is good--as is an ice cube made with one of those new spherical ice cube makers like this. Find a big enough one, and roll that around under your foot. Ice and massage all in one. :)
I'd say cut it with water instead of throwing an ice cube since you can control the amount of water more accurately. If you go ice cube route, the bigger the surface area the better! You can always use the smallest tupperware cup you got, makes for good ice makers as well!
But have fun w/ it. I typically have a sip of it straight up and cut it w/ the slightest bit of water, I'm talking like, 3-4 drops in a finger of scotch. Sip. Repeat. You'll be amazed by how water will change the character of the drink. I'm by no means a professional drunk but I love my campfire scotches!