If you have limited desk space or use a keyboard tray, try The Office Small.
If you are a minimalist and don't use a mouse pad, have a favorite mouse pad that you don't want to give up, or use a track ball mouse; try The Arm Mat.
If you have a large enough desk, go for The Full Desk (15in tall) or Full Desk Slim (13in tall). It is sleek and comfy for both arms at any time (because if only one arm feels comfy, the other arm gets jealous). This one is the ultimate in desk comfort.
If you are in media production and do a lot of wide "scrubbing" (and have the large desk space) you may like The Gaming Standard or Gaming Slim
If you are a performance gamer where The Office Executive won't suit your game genres, you can choose between the larger Gaming Standard, and The Gaming Oversized, which is 4 inches wider than The Gaming Standard to allow for even larger sweeping motions. The Full Desk is always an option as well if you really need some extreme real estate with some amazing comfort.