Isopropyl alcohol, the highest % you can get.
* This goes for GPUs too
It is also a very good cleaning agent and often used for cleaning electronic devices such as contact pins (like those on ROM cartridges), magnetic tape deck and floppy disk drive heads, the lenses of lasers in optical disc drives (e.g. CD, DVD) and removing thermal paste from CPUs*. It is also used to clean LCD and glass computer monitor screens (at some risk to the anti-reflection coating of the screen), and used by many music shops to give second-hand or worn records newer looking sheens. It cleans white boards very well and other unwanted ink related marks. Isopropyl alcohol also works well at removing smudges, dirt, and fingerprints from cell phones and PDAs. It is effective at removing residual glue from sticky labels.