A 'like' feature would be great, plenty of forum lurker types might be more likely to express their opinion with that one click.
For emoticons, I was thinking of just a few extras... I tend to use a thumbs up one quite often. Also something to indicate that you are joking other than the tongue out 'yellow head' (one site uses an animated set of three 'yellow heads' re-enacting the three stooges). And maybe a 'devil-horn' evil one would be good...