That really all depends on exactly what you are doing with it.
If you are wanting to watch movies on your new TV, you will likely want a BluRay player, which can play BluRay movies, DVDs and music CDs. In fact, a BluRay player will enhance the DVDs so that they look better than if played on a standard DVD player. Also many BluRay players allow you to stream content from sources such as Netflix, and Pandora.
For each HD device (cable/satellite receiver, game system, BluRay player, etc.) you will need an HDMI cable. The cables typically do not come with those devices, and certainly do not come with the TV. Do not be fooled, not all HDMI are the same. The low-end brands will not carry as much information from your device to your TV. So devices that push more information, such as satellite receivers, need better cables. I have a Monster 1000 series on mine (the Monster 1000 series is equivalent to the current Gold series). And I have a Rocketfish brand HDMI cable on my BluRay player because it sends less information to the TV.
Like HDMI cables, not all surge protectors are the same, either. The best is absolutely worth it in this case. Personally I prefer the Monster 900c PowerCenter. It offers great protection, but more than that extends the life of your electronic devices. I'd rather buy a TV every 10 years and not every 3-5 years.
Something often overlooked by first-time purchasers of HDTVs is sound. The speakers on most new HDTVs are #1 on the back of the TV and #2 very under-powered (10-20w). So, even turned all the way up they don't produce much sound, and what sound they do produce doesn't have much audio range (no high "highs, no low "lows). So either a surround sound system or a soundbar becomes necessary for any TV not going in a bedroom or kitchen, and even then sometimes in those rooms as well depending on circumstances. For the sound equipment, a Digital Optical cable will be necessary. Some come with the cable, but most do not, and the ones that have an included cable use cheap cables. So getting at least the Rocketfish Digital Optical cable is a good idea for your sound equipment.
And, depending on your room layout, mounting your TV might be crucial. I always consider only full-motion or tilt mounts, and never low-profile because of the difficulty in using those and the glare they can cause.
Some people like to go cheap on these types of items, but really this is a one-time purchase for your TV. So it is worth it to get quality items that won't break the bank.