NightOwl (was YoruFukurou) is a powerful native Twitter client for Mac OS X

Features:

• Manage multiple Twitter accounts
• Create tabs from rules (user IDs, keywords and regular expressions)
• Create Twitter search tabs
• Create tabs from Lists
• Block unwanted Tweets (user IDs, keywords, regular expressions and application name)
• Powerful keyboard shortcuts
• Conversation view
• Single user view
• Change font size
• Unread management (hit space key to read through unread Tweets)
• Powerful notification support (sound and growl)
• Two different appearance modes (normal view and mini view)
• Image preview
• "Paste to YoruFukurou" bookmarklet for web browsers
• Autocompletion (user IDs and hashtags)
• Now browsing & now playing
• Upload images
• Customizable image service
• Instant filter
• URL shortening
• Customizable URL shortener
• Translation
• Show one-sided follow badge
• Color customization
• API Error console