These Globular Clusters are all showpieces, presented in the order of their eyepiece impression. Unfortunately, for Northern hemisphere observers, most globular clusters reside in the southern half of the sky, including most of the finest globular clusters.
The second-brightest globular cluster is 47 Tucanae, and the second-largest, but it is the most dramatic in the eyepiece. Its dense core is clearly yellow in bigger scopes, due to the concentration of red giants massed there.
Omega Centauri is the brightest and biggest, but it is rather lacking in individuality, except for the two darker patches within it. It is a huge rich oval of uncountable stars, but some consider it lacks central condensation.
Located in Pavo, NGC 6752 is the fourth-brightest globular cluster. Arcing star chains converge to a small central pip.
M13 is only the eighth-brightest, but with its long star chains & propellor-like dark lanes, the Great Hercules Cluster is perhaps the most distinctive in appearance. It is generally considered by observers to be the finest globular in the northern half of the sky.
This is the fifth-brightest and third-largest. Its central bar and loose structure make this the only candidate for the title of most distinctive. M4 is currently thought to be the closest globular cluster. Consequently, it is one of the easiest to resolve.
M22 is the third-brightest. Even a 2 inch (50mm) refractor resolves a few stellar pinpoints.
M15 rises to a remarkable sharp cone, like a classic volcano cone.
This globular cluster, NGC 2516 in Columba is much like M15, but fainter.
NGC 6397 in Ara, is the second-clostest, and the easiest to resolve.
M55 in Sagittarius ranks next, but NGC 2808, M3, M5, and NGC 6541 all have good claims to rank in the top ten.