6.5x55 is not super common here, but has its adherents... rabid ones! I bought one for my wife. It is a superb cartridge, and if I could have only one medium caliber RIFLE, it would be in my top 5 choices. .308, .30-06, 7mm mauser or 7.92 mauser would be the others. 6.5x55 and 7mms are probably the best balanced, realistically.
If I could only have ONE centerfire cartridge rifle, the traditional choice would be .375 H&H. Though handloading would be required for some roles;-)
Sorry, rambling digression over