Push Ups.

ahhh...on average?  30-40.    but man, I sometimes just do 10 10 times in a row.  I never really cared on the set. 

Or, try this, start with 5, stop for 30 seconds, then do 10, then do the same, then do 20 and so on and so on. 

It's pretty interesting

Or, do it backwards.  You said you usually do 25 a set.  Cool.  Start with 25 then go down, 20, 15, 10, 5.  That right there is 75 push ups

and all done in probably less than 10 minutes.

You don't want to start your muscles going then stop them pickyourpocket, that's how you tear a muscle.

I've never torn a muscle

When you bench, you don't do a set of 10 then stop?   Then go after at least a minute for another set?

Or even sit-ups.   if you do 100 sit ups you don't stop? 

Then start up again? for another 100?

My new goal should be 500 pushups everyday. Then I can become more than One Punch Man.

UHHHH haven't I been saying that? 

I always try it when I'm asleep. But most of the time I'm too tired to do it.

Will i get o er 9000?

I think 25 are already impressive. 30 next?

35+ push up in good day. ( no training now, 25 I guess)

Diamond pushups add a little more challenge. I used to work on one-arm, gradually lowering height down steps of a staircase. It took me a number or months to reach the bottom, but it was a rewarding achievement. It's the kind of thing I practiced frequently with no more than 5 reps. I was following a book by Tsatsouline at the time.