A nice and useful exercise I made with chords is to play them in reverse quinte succession. In many musical style, maybe all, you will find progressions like V-I, II-V-I, VI-II-V-I, and so on. If you begin with the IV, it will give you: IV-VII-III-VI-II-V-I
You can harmonize it and play, as example in A-:
|:D- |G76 |Cmajor7 |Fmajor7 |B half diminished | E7b9 |A- |A- : |
I am a lazy bastard and I like these kind of exercise, that because it is an exercise and it sound as a song.
Also the best exercise I found for guitar practice are the one at the beginning of Juan Serrano - Flamenco Guitar Basic Techniques.
It's flamenco for beginners and that's the best guitar technique I now, that because mediator picking learn us to push and pull strings in rhythm with one piece of plastic, classical picking technique learn us to pull the strings in rhythm with the 5 fingers, and flamenco picking technique is superior because it learn us to push and pull the strings in rhythm with the 5 fingers.
You must begun very slowly to be in rhythm, and accelerate as soon as you can. The most important is to be in rhythm, even when you miss a note, just continue in rhythm. Also, whatever picking technique you choose, it is a very good habit to play the rhythmic of all your song in arpegio (just play the chords in arpegio) with that picking technique, that because with time, it will naturally help you for both solo and rhythmic playing.
Maybe the most important for me: try to play everything in rhythm, no matter what rhythm you choose or can. That way, you will exercise the rhythm with all the other exercises. Again, I am a lazy bastard and if I can exercise several things with 1 exercise instead of 2 or 3 or 5, I will always choose to do it with 1.