When you buy a good quality tripod, you just get the tripod legs. A good quality ballhead can make all the difference in capturing great looking landscape or nature images. A ballhead will let you quickly and easily adjust where your camera is pointed and how it is oriented (horizontal or vertical). Its also the most secure means to hold that expensive DSLR and lens you’ve just paid good money for.
The folks at Really Right Stuff make the best ballheads and arca-swiss style clamps I’ve ever used and the unit shown below is their BH-40 LR (BH-40 head with B2-40 LR clamp). It fits perfectly on my Gitzo Traveller tripod legs and keeps my Canon 50D perfectly still when taking nature shots. It’s also a great ball head for basic pano shots as well.