Masteries to NOT take. (In Ferocity)
Of course these are just my thoughts but lets look at the mastery tree's and see which ones you should NOT take. http://gameinfo.na.leagueoflegends.com/en/game-info/summoners/masteries/
Starting out in the Ferocity vein: Feast: Reason being that this only gives you an extra 20HP every 30 seconds at max, IF you kill a minion. Looking at the other two options you either gain 3% damage or give 3% damage to each of your allies when you cause some damage. At 20HP per 30 secs you lose all of that in one AA from pretty much any champ and they can AA you more often than 30 seconds. This is just a bad choice that is in desperate need of a rework.
Expose Weakness vs. Double Edged Sword: Honestly to take anything except Expose Weakness is a fairly selfish move. It's really up to you which you take but think of it this way. If any other player on your team takes Expose Weakness, you're gaining that 3% damage in a team fight without taking an additional 1.5% damage. You're also giving them 3%. That can be a total of 15% total damage increase on your team without any real draw back. Think the team game, not the solo game. This isn't all 1v1.
Next I'll skip a few to the Bounty Hunter / Oppressor level: If you take Oppressor you're gaining a 2.5% increase in damage pretty well off the start. Any slow, BOOM power burst. However you're more than likely going to kill at least 3 unique champions in a game. Taking the Bounty Hunter mastery will give you greater damage output in the long run. Play safe, get them kills, and take Bounty Hunter.
That's all for the Ferocity vein. Will get back with thoughts on the other two in the future!