Slim has some good points there. Full-contact incorporating disciplines/arts like krav, muay thai, kyokushinkai, boxing, kickboxing,savat et.c. may help with conitioning, increasing your resilience as well as giving you some good weaponry
Not to say other thinmgs don't have their merits. On the contrary, many MA (especially Japanese ones - gendai budo mostly; koryu are a different animal all together) have many things to offer that the aforementioned do not but they are not as quick to get to the skull-cracking stuff. Better pursued as long term goals.
P.s. not to get in a debate over kata here but there is a reason they had bveen the foundation of japanese koryu for almost 800 years. Open sparring was a later development in most arts, long after the Sengoku Jidai period where the technically more effective forms had died down in favour of more modern non-battlefield forms.