There are two Unicorn Peaks in Washington - this Unicorn Peak is in the Tatoosh Range in Mount Rainier National Park. Unicorn Peak is a committed alpine climb - it can't really be considered a hike.
It's recommended you prepare carefully reading guidebooks and climbing websites, and making sure you have the necessary skills, experience and equipment. You will need to be able to handle wilderness route finding, high angle snow ascent and descent, rock climbing, and challenging terrain. Adequate physical conditioning is critical to ensure success and safety. Each of your party members needs to prepare in kind. Study the weather and conditions right up to your departure as these can change rapidly. (See the trip report by KD7LXL here: http://www.pnwsota.org/node/249.)
You'll take the trail to Snow Lake from the namesake trailhead (46.7678, -121.7071 - note that parking can be challenging on summer weekends) and find the end of the maintained trail at Snow Lake after about 1.5 miles. From here you'll need to have good navagation skills and a route description to make your way towards the summit. Depending on the season, you'll cross a boulder field to access the first of several steep snow pitches up to a saddle with great views of Mounts Rainier and Adams. Note that the SOTA coordinates of Unicorn Peak is perhaps 125 meters south of the actual summit.
It is possible to forgo the final ascent of the 50 foot Class 4 to 5 summit block and be in the Activation Zone. There are rocks to support poles for antennas. There may be very little 2m FM activity in this remote section of Rainier National Park and so you should not depend on making four contacts with an HT - our party only made one, despite many calls on multiple frequencies.
More information here: http://www.summitpost.org/unicorn-peak/151196.
