I like the "old" 80s and 90's style uniforms (silver pants, Totem armband, silver helmets). Of course, that's because the 'hawks got those new uniforms in 1983 when Chuck Knox came to town and turned around the franchise, and I guess part of me always associates that uniform with Chuck Knox.
The two uniforms I like the least are the original "Chicago Bears Style" unis from 1976-1982 and the all "gunmetal blue" unis of the 2000s (although the whites weren't so bad....except we always seemed to lose in them).
I happen to like the new (2012-present) uniforms. I initially thought I wouldn't but I have to admit that the uniform as grown on me. Love the wolf uniforms.
My least favorite uniform of all time are the "neon greens" we wore under Mora Jr at home against Chicago. Those were an abomination.