I'm the resident Fitbit fan at Android Police - I had the One for more than 3 years before I switched on to the Flex 2 and Alta HR for the past year. I love the automatic tracking and the nerd in me appreciates all the stats and graphs about my habits. I also enjoy the community around it. For me, the idea behind activity trackers isn't that they will make you more active - that's the mistake everyone makes and why many give up on their trackers after using them a while - but it's that they will help you if you already made the decision to be more active. They can gamify the experience and add a more concrete proof of your progression, whether you're just playing against yourself and trying to improve your numbers, or you're competing against friends or family or strangers.
With that in mind, if you want to get an activity tracker for yourself or as a gift, now's a good time to do so. Three of Fitbit's current trackers are discounted $50. If you want a do-it all, I recommend the Charge 2: it was the best all-around tracker when I reviewed it a year ago and at $99, I still think it is. If you prefer a more streamlined look with better battery life and don't mind some compromises, the $99 Alta HR is fantastic and it's the one I'm still wearing now since reviewing it in April. And if you really, really, really want something that looks like a smartwatch, there's the $149 Blaze. Value for dineros, I personally think your money is better spent on the Charge 2 with $50 to spare, but the Blaze is good and has improved a lot since I reviewed it last year.
You can grab any of these from Fitbit's site or through the links below. Keep in mind that all trackers come in different colors and band sizes, so please choose the correct one.