The Tank theme is super clean and minimal. It's great for lightweight sites that want a minimalist vibe.
Neo is clean, powerful, and rich with features. A great theme for an RIA that has dynamic content (like a blog and podcast) and wants to feature media mentions.
The Morpheus theme has a lot of flexibility for various marketing content. It's also a good theme for larger sites because the off-canvas navigation can hold lots of items.
Cypher has some unique CTA layouts and interesting features. It's great for a site with lots of great photos and visuals.
Agent Smith is a striking, edgy theme that has a unique look and feel.