Here are some sentences that contain two words that are reversible.
(Please only answer 5 to give others a chance, thanks! If it goes into a second day, feel free to finish them off.)
1. ____ is as selfless as I ____. [Ma/am - sarajean]
2. There is a ____ of leftover stew on the ____ shelf of the refrigerator. [pot/top - Bev Vincent]
3. ____ is well-known that "____" is the note after "la." [it/ti - Bev Vincent]
4. The beaver got ____ at animals that disturbed his ____. [mad/dam - Bev Vincent]
5. I was so hungry that I ate my ____ sandwich on the ____. [sub/bus - Goblin]
6. Kittens are great ____ as long as you don't ____ on them. [pets/step - Bev Vincent]
7. I went to ____; then I dreamed about clowns tripping on banana ____. [sleep/peels - sarajean]
8. The rock ____ kept mice and ____ as pets. [star/rats - Jean]
9. Sometimes a ____ of calamine lotion can soothe a ____ itch. [dab/bad - SigTauGimp]
10. The ____ ____ not in the tool shed where it belonged. [saw/was - Jean]
11. The quick brown fox said, "____ no!" as the riders yelled, "Tally ____!" [Oh/Ho - sarajean]
12. It's ____ to stay off ski lifts and ____ while they're being repaired. [smart/trams - Crunchy]
13. The best ____ of the story was watching the hero ____ the spy. [part/trap - sarajean]
14. There was some ____ stuck on Mom's coffee ____. [gum/mug - Bev Vincent]
15. Yes, you ____ have another ____ after you finish your turkey. [may/yam - flaggwalkstheline]
16. The bully had no friends because he always tried to ____ his ____. [slap/pals - Lily-sai]
17. My aunts sometimes make a big ____ over who ____ a better sweater. [stink/knits - Gaberax]
18. My chihuahua is a great ____ so I let him sit on my ____. [pal/lap - sarajean]
19. We ____ about to study the ____ of the dinosaur. [are/era - Jean]
20. After ____ tries, I finally served the ball over the ____. [ten/net - SigTauGimp]
21. Dad wanted to ____ my paper about how the ____ is affected by the moon. [edit/tide - Jean]
22. When my uncle is in a bad ____, he talks about gloom and ____. [mood/doom - J&Y]
23. I'd rather ____ for gold than take a ____. [pan/nap - Goblin]
24. There's a rumor that ____ people ____ in the old house. [evil/live - Jean]
25. The mail carrier was ____ by his boss for failure to ____ the mail on time. [reviled/deliver - Gaberax]
26. A ____ that's heaver than air will ____ down to the bottom of a mineshaft. [gas/sag - Lily-sai]
27. Even a heavy television set does ____ weigh a ____. [not/ton - Goblin]
28. He ____ yesterday but he's losing right ____. [won/now - J&Y]
29. Mom secured the bicycle ____ to the luggage rack with a thick ____. [parts/strap - Jon]
30. If you think that silly mask will ____ anybody, you're ____. [stun/nuts - Gaberax]
31. I didn't ____ washing the ____ until they were completely clean. [stop/pots - J&Y]
32. I ____ up my skates and took a speck of mud off the gold ____. [laced/decal - J&Y]
33. I'd never ____ a pet with ____ for one with fins. [swap/paws - Jean]
34. I got a ____ that eating the inside of a peach ____ is bad for you. [tip/pit - Goblin]
35. My little brother plays with ____ toys, ____ I outgrew them. [tub/but - J&Y]
36. Uranium can ____ a lot of radiation over a long period of ____. [emit/time - Goblin]
37. If I ____ you on the shoulder, please pass me a ____ of butter. [tap/pat - Gaberax]
38. I'm sure it's hard to train a ____ to push the ____ key. [bat/tab - Jean]
39. You're more likely to find swimming ____ on an ocean liner than on a ____. [pools/sloop - Gaberax]
40. Sports-car owners like to ____ their ____ exhausts. [laud/dual - Crunchy]
And that's all, folks!