I picked the .303 and .375 merely on the basis of actual use over the last hundred or so years and that they are British. British being a criteria of the comment.

Non British, obviously the .30-06 would be up there at the top.

I've only got two .303's both Mk1 No.III SMLE's. One full wood, still with matching numbers. Mainly purchased this for heritage reasons. Would be cool to have it displayed hanging on a wall. Nowadays not possible until I one day build a man cave walk in underground bunker where it and others can hang on a wall.

The other is a cut down version. For rough use. Also an original Light Horse scabbard. In case I need to ride a horse one day ...

One day I think it would be nice to have a nice classic sporting .303 and use it for hunting. Maybe a Lee Speed or a double in .303.