Sports that translate to boxing.

[AdamGB]

From a physiological point of view - tennis, a lot of lateral movement/footwork and the various movements at the shoulder girdle when striking with a racket aren't dissimilar.

Both are fairly anaerobic and a lot of the tactics involve out angeling your opponent without telegraphing your intentions.

[Bo-Bo24]

No sport. A fight down the pub is completely different to a fight in the ring.

[goti71]

Interesting thread.
Footwork, positioning and circling your opponent in historical fencing or in any sport using weapons (trick fighting, quarterstaff, etc.) translates very well to boxing. Also things like feinting, short punches, not swinging wildly, etc.
I tried a hand at historical fencing and it felt the same in that sense. Even though the stance was southpaw when holding a one-handed weapon like a rapier, it didn't really matter.