I would strongly prefer a logo that does *not* include the following stereotypical legal elements: (1) a gavel, (2) the scales of justice, (3) the columns of a courthouse. They are way too overused. I'll still consider a logo that contains one of these, but it would have to be pretty damn creative.
I'm more receptive to abstract graphical elements, whether they evoke the name of the firm or not. Car manufacturers don't have pictures of cars in their logos---the abstract designs work just fine for brand recognition. If you'd like to include a graphic that actually evokes a physical thing, I'd suggest:
--broken handcuffs (symbolizing freedom)
--the silhouette of a suit and tie
--the Houston skyline
--the Harris County Criminal Justice Center building
--the shape of the State of Texas (abstracted)
--The Come and Take It flag (interesting to see if anyone could do something with this---it's a challenge)
Don't feel bound by this list. Purely abstract symbols are still fine. I'm sure I'll see what I really like as the contest continues. The point is that all of these are more memorable than a gavel.
As for colors, I leave it up to you. Not everything needs to be muted reds, blues, and neutrals. If you think you can make a classy brand identity with green or orange or purple or whatever, go for it.
Update: I appreciate the tie designs guys, I do. But let's not get too copy-catty or one track minded. I'm still very open to (and rated well) some other abstracts. I also haven't seen attempts at some of the (nonexclusive) suggestions above.