Hunting down the Andromeda Galaxy globular clusters can be challenging, but it is a lot of fun.
The brightest is known as G1, and is at a magnitude of 13.5.
Use my guide to help you identify this and some of the other globular clusters swarming around our neighbouring spiral galaxy. http://www.star-gazing.co.uk/Downloads/AndromedaGlobulars.pdf
Image below. G1 globular Cluster (Dave Eagle).