Certainly! Here's a list of commonly used Excel formulas with examples for daily office tasks:

1. **SUM:**
```excel
=SUM(A1:A5)
```
Adds up the numbers in cells A1 through A5.

2. **AVERAGE:**
```excel
=AVERAGE(B1:B10)
```
Calculates the average of the numbers in cells B1 through B10.

3. **IF:**
```excel
=IF(C1>50, "Pass", "Fail")
```
Checks if the value in cell C1 is greater than 50; returns "Pass" if true, "Fail" if false.

4. **VLOOKUP:**
```excel
=VLOOKUP(D1, E1:F10, 2, FALSE)
```
Searches for the value in cell D1 in the first column of the table E1:F10 and returns the corresponding value from the second column.

5. **HLOOKUP:**
```excel
=HLOOKUP(G1, H1:M5, 3, FALSE)
```
Searches for the value in cell G1 in the first row of the table H1:M5 and returns the corresponding value from the third row.

6. **INDEX and MATCH:**
```excel
=INDEX(K1:K10, MATCH(L1, J1:J10, 0))
```
Returns the value in the range K1:K10 corresponding to the match of the value in cell L1 in the range J1:J10.

7. **CONCATENATE:**
```excel
=CONCATENATE(A1, " ", B1)
Combines the text in cells A1 and B1 with a space in between.

8. **LEFT:**
```excel
=LEFT(C1, 3)
```
Extracts the first three characters from the text in cell C1.

9. **RIGHT:**
```excel
=RIGHT(D1, 2)
```
Extracts the last two characters from the text in cell D1.

10. **LEN:**
```excel
=LEN(E1)
```
Returns the number of characters in the text in cell E1.

11. **TRIM:**
```excel
=TRIM(F1)
```
Removes extra spaces from the text in cell F1.

12. **DATE:**
```excel
=DATE(2023, 1, 15)
```
Creates a date for January 15, 2023.

13. **NOW:**
```excel
=NOW()
```
Returns the current date and time.

14. **COUNT:**
```excel
=COUNT(G1:G20)
```
Counts the number of cells with numbers in the range G1:G20.

15. **COUNTIF:**
```excel
=COUNTIF(H1:H15, ">50")
```
Counts the number of cells in the range H1:H15 that are greater than 50.

Feel free to adapt these examples to your specific data and requirements in the office.