Depends on my affiliation.
If I fought for the NCR:
I would offer my services as an off-the-books soldier to the NCR. Judging by my sterling reputation with them, I could make a killing (heh pun). I'm sure I'd either end up retiring a wealthy man or end up lying face down in a pool of my own blood.
If I fought for the Legion:
I would probably try to work my way to become the right-hand man of Caesar so when the time came, I could assassinate him and take control. Bowing to tradition, I would adopt the title "Caesar" and start a campaign in the East in the attempt to eventually forge Caesar's Legion into a continental empire.
If I fought for House:
I'd be sitting pretty in Vegas and rolling in caps. What else would there be to do?
If I fought alongside Yes-Man:
I'd start my own nation. The Vegas Confederacy. I'd annex outlying territories through shrewd business tactics but leave them relatively independent. I wouldn't want them to be too closely affiliated with me though. That way, if they become a problem, I can just cut them loose and let them suffer until I could regain control. I'd use Yes-Man as a diplomat of sorts since he couldn't really be killed.