I'm interested to know if anyone utilizes assessment tools for front-line employees that align with your company's core values? Do you employ any quizzes or services to evaluate soft skills behavior that reflects your values, such as demonstrating integrity consistently, delivering results through diligence and a commitment to excellence, and acknowledging the success and accomplishments of others?

This is a great question.  I have used DDI World - they have tool that are role specific.  You have to warn people not to rush the process so the assessment truly reflects who they are and what the gaps may be.  

I also use Everything DiSC - workplace on Catalyst and use the report during onboarding to level set and establish "common" language or operational definitions for my team and our organization.  From there, you can build upon that foundation with "The Work of Leaders", "Management", Productive Conflict", "5 Behaviors of Cohesive Teams", and "AgileEQ or Emotional Intelligence".  

Lastly, on the recruitment side, when there is a panel, I have found structuring the questions with embedded values based questions and suggest candidates use the STAR method enables you to really unpack responses to discover points of connection, and disconnect.

I have developed a structured interview tool for recruiting frontline staff.  Here are the key steps taken:
1.  Gather a tool of top performing sales staff.  (* If time and resources allowed, you can also gather a group of non-performing sales staff to identify differences in response in the later stage of the project. )
2.  Identify unique and common skills and competencies of the group.
3.  Develop a set of structured interview questions and identify the most reliable and valid responses from the group that differentiate them from other candidates.  This process require thorough analysis of the questions and response.
4.  A standardized questionnaire was developed after thorough testing and is used in subsequent interviews which proved to be effective as it reduces the chance of biases.

For certain jobs that may require specific skills (e.g. logical thinking), you may consider choosing additional aptitude tests to further strengthen the filtering process. 

Hope this helps!