Sentinel for me - I love having access to biotics and tech. Sentinel is a well-rounded class that can work well with any teammates. It's a fun class in all 3 games, but in 3 it's amazing - 90% damage resistance with fortification (soldier ability) completes the class with all 3 types of moves, access to all weapon types, and 60% increased power damage and force from armor abilities alone. Can't wait to see how Andromeda's new system works, would be awesome to have a sentinel with more access to soldier abilities as well. All the classes are really fun in 3 and I could play any of them and have a good time. :)
Easily my least favorite companions are Javik and Zaaed. Their cruelty and arrogance are annoying and I can't get past it. Javik's attitude to Liara is completely unnecessary and it's a shame because he's tainted my entire perspective of Protheans. I actually really like Traynor and Cortez (especially Cortez) and I personally don't find them generic at all. Jacob is boring but tolerable and easy to get along with. Tali is mixed for me, she's alright and I like her well enough but I don't get the obsession with her (nothing against anyone who loves her character). James grew on me and I find him to be fun for what he is on paper (generic soldier). Ashley's xenophobia also really bothers me, lots of people find Kaidan to be boring but I like him far, far more than Ashley.