I love to be statistically in advantage with a pair, that boost my confidence pre-flop.
However, if I start with a big pair, i'm tempted to be more aggressive than necessary. I risk being even all-in pre-flops and the opponents can often catch something better than my starting pair.
In contrast, if I start with a small pair, I'm too inhibited and tight, risking to play too scared.
So, my favorite pair is tens, because it gives me balance in my game and I have a better chance of making more right decisions depending on the style of the players I face.