I play almost exclusively with encore mallets. Their Nanae Mimura and Nancy Zeltsman series of mallets are great. They seem to hold up quite well too. The Nanaes have a little bit of a darker sound and are a little lighter to hold. I prefer the brighter sound of the Nancy Zeltsman series, and they are a little heavier. The NM3, and the NZ3 seem to be the best all around mallets.
Mallets I like from other companies are the Michael Burritt Malletechs, and the IP soloist line. Also, Mike Balter's blue vibe mallets absolutely ROCK on the marimba. They have a bit of a short shaft, that is actually nice in some situations. Definitely worth having in your arsenal.
Also, I heard Black Swamp was importing Inaki Sebastian mallets. I would like to hear a review of those. They look really sweet.