At the risk of sparking a flame war, any CHDK capable Canon with reasonably good low light sensitivity would *do*, but as lapser has demonstrated, good low light sensitivity is important.
It all depends on your budget and possibly the risk to the camera. If you are going to leave it unattended, then weather and wildlife (and human life) might prove its undoing. I might risk leaving my battered Ixus 60 in top of a mountain over night in a weatherproof box, but I am not so sure I would leave an expensive new G1X (or even my Ricoh CX3) to potentially share the same fate.
Even something like the humble Powershot A2200 should be able to give good results.
If you are going for a new camera, rather than second hand, get one with a backlit CMOS sensor (If you are on a more limited budget than the G1X, any Point and Shoot Ixus model ending in HS, for example the Ixus 115 HS, would probably do well).
I would venture further and say that any Canon that can take pictures with a higher resolution than 1080p (approx 2.1Megapixels) will theoretically be able to produce good time lapse results, if you don't need to "see in the dark".
There are some impressive time lapses shot on the A560, and the Ixus 60, and these are not exactly high resolution by todays standards, but in my experience they can shoot well in relatively low light.
The Ixus 105 also takes reasonably good pictures in low light (but its inbuilt movie mode is absolutely lousy in poor light).
You are after all taking lots of photographs and combining them in to a movie, rather than relying on the movie capabilities of the camera. Sharp optics and (for sunsets and the like) good low light capabilities are all you need, and most of the Canon point and shoots *should* fall in to this bracket.
Good light sensitivity will allow the camera to use lower ISO settings shorter exposure times per frame, and thus minimise motion blur and noise. The G1X will undoubtedly produce superb results, but I would venture in light of what I have said above, that with a little bit of tinkering, some of the more budged models will not be far behind.
