Boggle- This is by far the most popular in my room. I got this amazing activity from Create-Teach-Share and my kids go bananas for it. I just change the letters weekly to reflect our spelling pattern focus and they go on a word making frenzy. LOVE it!
Super easy math warm-up (would need to be modified for Kinder). You could also differentiate this by including harder questions at the end for students who can quickly complete the first few questions.