I swing trade futures long/short holding for days/weeks/months - up to 8 different contracts at any given time. First of all you need a solid risk mgmt plan for swing trading futures - I never risk more than 1% of capital on any trade or have more than that exposed in the over night market on the sum of all positions. The only contracts I will not trade are live-stock because I am vegan and O.J. because of the movie 'Trading Places'. I like stock indexes since that is were I started out on - they offer a lot of data like sentiment, internals, and react well to seasonal influence.
The protection comes from being properly capitalized and having a real good risk mgmt plan that you follow perfectly - every time. I think you need at least $100K for this but might be o.k. with maybe $50k trading the contracts with smaller price moves. I am very aggressive in cutting out losses fast and locking in a break even point on new trades. I use mostly a mechanical system which also helps - everything I do is a process that is well planned out. Kowing your plan inside and out including how you plan on dealing with draw downs is key to make it long term. A good book from one of the best futures swing traders is 'Diary of a Commodities Trader' - Peter Brandt.
Here is a list of the most common futures contracts I trade to give you an idea.