Some Google Scripts I used to run periodically on my Gmail. Saving for posterity.

awaiting_response.gs

/*
 * This script goes through your Gmail Inbox and finds recent emails where you
 * were the last respondent. It applies a nice label to them, so you can
 * see them in Priority Inbox or do something else.
 *
 * To remove and ignore an email thread, just remove the unrespondedLabel and
 * apply the ignoreLabel.
 *
 * This is most effective when paired with a time-based script trigger.
 *
 * For installation instructions, read this blog post:
 * http://jonathan-kim.com/2013/Gmail-No-Response/
 */


// Edit these to your liking.
var unrespondedLabel = 'Awaiting Response',
    minTime = '5d',   // 5 days
    maxTime = '14d';  // 14 days

// Mapping of Gmail search time units to milliseconds.
var UNIT_MAPPING = {
    h: 36e5,    // Hours
    d: 864e5,   // Days
    w: 6048e5,  // Weeks
    m: 263e7,   // Months
    y: 3156e7   // Years
};

function awaiting_response() {
  processUnresponded();
  cleanUp();
}

function processUnresponded() {
  var threads = GmailApp.search('is:sent from:me -in:chats older_than:' + minTime + ' newer_than:' + maxTime),
      threadMessages = GmailApp.getMessagesForThreads(threads),
      unrespondedThreads = [],
      minTimeAgo = new Date();

  minTimeAgo.setTime(subtract(minTimeAgo, minTime));

  Logger.log('Processing ' + threads.length + ' threads.');

  // Filter threads where I was the last respondent.
  threadMessages.forEach(function(messages, i) {
    var thread = threads[i],
        lastMessage = messages[messages.length - 1],
        lastFrom = lastMessage.getFrom(),
        lastTo = lastMessage.getTo(),  // I don't want to hear about it when I am sender and receiver
        lastMessageIsOld = lastMessage.getDate().getTime() < minTimeAgo.getTime();

    if (isMe(lastFrom) && !isMe(lastTo) && lastMessageIsOld && thread.isInInbox()) {
      unrespondedThreads.push(thread);
    }
  })

  // Mark unresponded in bulk.
  markUnresponded(unrespondedThreads);
  Logger.log('Updated ' + unrespondedThreads.length + ' messages.');
}

function subtract(date, timeStr) {
  // Takes a date object and subtracts a Gmail-style time string (e.g. '5d').
  // Returns a new date object.
  var re = /^([0-9]+)([a-zA-Z]+)$/,
      parts = re.exec(timeStr),
      val = parts && parts[1],
      unit = parts && parts[2],
      ms = UNIT_MAPPING[unit];

  return date.getTime() - (val * ms);
}

function isMe(fromAddress) {
  var addresses = getEmailAddresses();
  for (i = 0; i < addresses.length; i++) {
    var address = addresses[i],
        r = RegExp(address, 'i');

    if (r.test(fromAddress)) {
      return true;
    }
  }

  return false;
}

function getEmailAddresses() {
  // Cache email addresses to cut down on API calls.
  if (!this.emails) {
    Logger.log('No cached email addresses. Fetching.');
    var me = Session.getActiveUser().getEmail(),
        emails = GmailApp.getAliases();

    emails.push(me);
    this.emails = emails;
    Logger.log('Found ' + this.emails.length + ' email addresses that belong to you.');
  }
  return this.emails;
}

function markUnresponded(threads) {
  var label = getLabel(unrespondedLabel);
  label.addToThreads(threads);
}

function getLabel(labelName) {
  // Cache the labels.
  this.labels = this.labels || {};
  label = this.labels[labelName];

  if (!label) {
    Logger.log('Could not find cached label "' + labelName + '". Fetching.', this.labels);

    var label = GmailApp.getUserLabelByName(labelName);

    if (label) {
      Logger.log('Label exists.');
    } else {
      Logger.log('Label does not exist. Creating it.');
      label = GmailApp.createLabel(labelName);
    }
    this.labels[labelName] = label;
  }
  return label;
}

function cleanUp() {
  var label = getLabel(unrespondedLabel),
      threads = label.getThreads(),
      expiredThreads = [],
      expiredDate = new Date();

  expiredDate.setTime(subtract(expiredDate, maxTime));

  if (!threads.length) {
    Logger.log('No threads with that label');
    return;
  } else {
    Logger.log('Processing ' + threads.length + ' threads.');
  }

  threads.forEach(function(thread) {
    var lastMessageDate = thread.getLastMessageDate();

    // Remove all labels from expired threads.
    if (lastMessageDate.getTime() < expiredDate.getTime()) {
      Logger.log('Thread expired');
      expiredThreads.push(thread);
    } else {
      Logger.log('Thread not expired');
    }
  });

  label.removeFromThreads(expiredThreads);
  Logger.log(expiredThreads.length + ' unresponded messages expired.');
}

needs_response.gs

/**
 * Adds a label to messages that are addressed to me from 
 * known contacts that I haven't responded to yet.
 */
var needs_response_label = 'Needs Response'

function main() {
  var contacts = ContactsApp.getAllContacts()
  var query = contacts.map(function (contact) {
    return 'from:' + contact.getPrimaryEmail()
  }).join(' OR ')
  
  Logger.log('running query: ' + query)
  var threads = GmailApp.search('to:me -in:chats ' + query)
  var thread_messages = GmailApp.getMessagesForThreads(threads)
  var needs_response = []
  
  thread_messages.forEach(function (messages, i) {
    var thread = threads[i]
    var last_message = messages[messages.length - 1]
    var last_from = last_message.getFrom()
    var last_to = last_message.getTo()
    
    if (!is_me(last_from) && is_me(last_to) && thread.isInInbox()) {
      needs_response.push(thread)
    }
  })
  
  // Mark unresponded in bulk.
  mark_needs_response(needs_response);
  Logger.log('Updated ' + needs_response.length + ' messages.');  
}

function is_me(fromAddress) {
  var addresses = get_email_addresses();
  for (i = 0; i < addresses.length; i++) {
    var address = addresses[i],
        r = RegExp(address, 'i');

    if (r.test(fromAddress)) {
      return true;
    }
  }

  return false;
}

function get_email_addresses() {
  // Cache email addresses to cut down on API calls.
  if (!this.emails) {
    Logger.log('No cached email addresses. Fetching.');
    var me = Session.getActiveUser().getEmail(),
        emails = GmailApp.getAliases();

    emails.push(me);
    this.emails = emails;
    Logger.log('Found ' + this.emails.length + ' email addresses that belong to you.');
  }
  return this.emails;
}

function mark_needs_response(threads) {
  var label = get_label(needs_response_label);
  var i = 0
  while (threads.slice(i, 100).length) {
    label.addToThreads(threads.slice(i, 100))
    i += 100
  }
}

function get_label(labelName) {
  // Cache the labels.
  this.labels = this.labels || {};
  label = this.labels[labelName];

  if (!label) {
    Logger.log('Could not find cached label "' + labelName + '". Fetching.', this.labels);

    var label = GmailApp.getUserLabelByName(labelName);

    if (label) {
      Logger.log('Label exists.');
    } else {
      Logger.log('Label does not exist. Creating it.');
      label = GmailApp.createLabel(labelName);
    }
    this.labels[labelName] = label;
  }
  return label;
}

remove_contacts.gs

/**
 * Remove contacts from the contacts API where I haven't saved the full name.
 */

function remove_email_contacts() {
  var contacts = ContactsApp.getAllContacts()
  contacts = contacts.filter(function (contact) {
    return !contact.getFullName()
  })
  .map(function (contact) {
    ContactsApp.deleteContact(contact)
  })
}