Polar F6. Counts calories, good underwater if you like to swim. It's quite reliable and I like that it's coded, if you use it at a gym it doesn't go all wacky if someone beside you is also using an HRM.
I have a Polar F6 and F11. I like the chest strap that comes with the F6 the best and usually use that with either watch. The newer one results in wonky or missed readings every single workout, which is irking.
I am hoping to get a polar hrm for christmas. I like the thought of having that extra motivator to get my heart rate up. That and I don't go to a gym I only walk/hike and at the end of this month will add a lot of snowboarding into the equation so I really am clueless to exactly how much calories I am/will be burning.