I support a company if they release products which I like and use and if the company looks after their customer, e.g.
Mizuno - Chosen for the look, feel and sound of the club. Everything about my MP-59's and my JPX 800 woods I adore. Also love their manufacture method and the information they share with the public.
Titleist/Srixon - Love their balls. They seem to last a fair while (durability) but also feel excellent when playing. Not had the same from other manufacturers.
Bunker Mentality - Love the style of their 'less wacky' range of clothing. I like the feel of quality clothing and tend to pt for bright colours often, however I don't like the scruffy/casual look on the golf course. BM have clothes for both of those styles. Also excellent customer service, returns policy, they're based in the UK and they have a fun attitude unlike many stuffy companies.
Ogio - I've owned two Ogio bags so far and neither has failed on me. I like the durability of the bags and the style of them.