Rocky peak just northwest of the Alpental ski area, on the Chair Peak ridge. This is probably the most popular summit rock climb in the Cascades, so beware of crowds and Mountaineers training climbs, but there's more than one worthy route to climb on any given day. Rock is volcanic and generally good.
Summer - Hike up the main trail until reaching a sign designating the start of the Source Lake Overlook trail. Take this trail, which minimizes elevation loss, to the valley to the south below the east face of The Tooth. There is a good climbers path with cairns to guide you.
Winter - Hike up the main trail all the way to Source Lake, then turn south in the valley. Hike up the valley until you are below the east face of The Tooth. Due to significant avalanche danger there, do not follow the summer path.