TweetDuck/Controls/FlatButton.cs

using System;
using System.Windows.Forms;

namespace TweetDuck.Controls {
	sealed class FlatButton : Button {
		protected override bool ShowFocusCues => false;

		public FlatButton() {
			GotFocus += FlatButton_GotFocus;
		}

		private void FlatButton_GotFocus(object sender, EventArgs e) { // removes extra border when focused
			NotifyDefault(false);
		}
	}
}